THE POSITION OF PERCOPSIS 
 
 BY 
 
 CLAUDE LEIST 
 
 A. B. University of Illinois 1918 
 
 THESIS 
 
 Submitted in Partial Fulfillment of the Requirements for the 
 
 Degree of 
 
 MASTER OF ARTS 
 
 IN ZOOLOGY 
 
 IN 
 
 THE GRADUATE SCHOOL 
 
 OF THE 
 
 UNIVERSITY OF ILLINOIS 
 
 1921 
 
Digitized by the Internet Archive, 
 in 2015 
 
 https://archive.org/details/positionofpercopOOIeis 
 
TABIJE OF CONTENTS 
 
 I. Introduction 
 
 II. The External Anatomy 
 
 III. The Internal Anatomy 
 
 1. Alimentary Tract 
 
 a. The mouth and pharyngeal region 
 h. The alimentary canal 
 
 2. The Sv;im Bladder 
 
 3. The Uro-genital System 
 
 4. The Nervous System 
 
 a. The brain 
 
 IV. Discussion 
 
 V. Conclusion 
 
 VI. Bibliography 
 
 VII. Explanation of Plates 
 
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THE POSITION OP PERCOPSIS 
 
 I. Introduction | 
 
 The position of Percopsis in its relationship among j 
 
 fishes has never "been definitely settled. From the time it was 
 first described by Agassiz to the present it has been placed by 
 ichthyologists within at least three divisions of teleosts, namely, 
 with physostomous fishes closely related to the Saltnonidae, with 
 the Haplomi , and with the Acanthopterygii. Gttnther places it in 
 his order Physostomi, in a family Percopsidae just above the Sal- 
 mon! dae. By most later ichthyologists it is thought to be a prim- 
 itive Acanthopterygian which has just made a transition from those 
 Physostomous fishes akin to the Isospondyli and Haplomi (Jordan 
 and Evermann) or an ancestral form of the present Acanthopterygians. 
 Boulenger alone places the Percopsidae among the Haplomi, of which 
 he says, ''They may be regarded as hi^ly specialized members (of 
 
 i 
 
 the Haplomi) having evolved in Ihe direction of the Acanthoptery- 
 gii.'' Goodrich agrees with Jordan and Evermann, while Regan, 
 
 5 
 
 thou^ he does not definitely place them, says the study of their 
 anatomy does not confirm the view that they are related to percoid 
 fishes of the Centrarchidae and Percoideae. 
 
 This paper deals with the anatomy of Percopsis guttatus; 
 
 its purpose being to determine more accurately the position of the 
 fish in the system. It describes the external appearances, the 
 

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 "brain, and the anatomy of the alimentary tract, uro-genital sys- 
 tem, and swim-bladder. An attempt was made to study thoroughly 
 the blood vascular system, but the state of preservation of the 
 specimens made that impossible. Some parts of the circulatory 
 system of the coelom and viscera could be made out, but that of 
 the head, the branchial arches excepted, was utterly impossible 
 with the material at hand. There was not time to study the skele 
 ton, so skeletal parts were ignored. However, the fact has not 
 been overlooked that the skeleton is of great importance in class 
 if ication. 
 
 II. The External Anatomy 
 
 Percopsis guttatus is a snail fish, rather slender, and 
 never attaining more than six inches in length. Of the thirty 
 odd specimens which I had, the largest measured not more than 5 
 inches in length (127 mm). The animal is sligihtly compressed and 
 tapers gradually posteriorly, terminating in a strongly forked 
 caudal fin. The depth of the body is about one-sixth of the total 
 length, or one-fifth the length if the caudal fin be not included. 
 The greatest width is conte-ined about eight times in the total 
 length, the width into the depth about one and a third times. The 
 greatest width of the body is just in front of the insertion of 
 the pectoral fin, the greatest depth sli^tly behind this inser- 
 tion, and the least depth is just in front of the caudal fin. 
 
 Thus the ratio of the greatest to the least depth is about three 
 
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 to one. Finely toothed ctenoid scales cover the tody with the 
 exception of the head, this "being naked. 
 
 The "back and dorso- lateral surface of the fish is a 
 sooty grey in color mottled with large "black spots. These "black 
 spots are placed in a linear arrangement the entire length of the 
 trunk and the caudal peduncle. The pignent of the skin is more 
 dense on the posterior part of the "body. The "belly is a silvery 
 white . 
 
 The lateral line organ appears as a white streak on the 
 "body. It is "bordered "by a dark pi^ent, and it first becomes 
 prominent at a point about midwe^y between the subopercular angle 
 and the dorso-median line. It extends posteriorly, keeping always 
 in the area of the dorso- lateral half and terminating just at the 
 base of the caudal fin. 
 
 The head is comparatively large, conical, and somewhat 
 broad. Large opercular openings give the head a broader s.ppear- 
 ance than it really has. The length of the head is one-fourth 
 the length of the entire animal; its greatest width when the 
 operculae are closed is equal to that of the trunk, but the depth | 
 is sli^tly less than the depth of the trunk. The width of the I 
 head is contained in the length about tv/ice, its depth one and || 
 
 two-fifths. The mouth is small and terminal, the upper margin | 
 
 protruding but sli^tly over tine lower. The upper margin is made 
 up of the premaxillary alone. The premaxillary is in length about 
 one-fourth that of the head, and the angle of the mouth is some- 
 what in front of and some distance below the nares. The nares 
 
-4- 
 
 are double. Each naris is divided by a partition giving an enter- | 
 and 
 
 io£/posterior aperture to each. They lie nearer the mid-dorsal ! 
 
 line than to the dorsal margin of the eyes, but are sli^tly nearer I 
 
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 the eyes than to the tip of the snout. The eyes are lateral and 
 a little high upon the head. The ventral margin of the eye is 
 above the middle of the side of the head; its diameter is a little 
 less than one-half the depth of the head, v;hile the inter-orbital 
 space is one-half the width of the head. There are six bran Chios t- 
 egals; the opercular openings are wide; the gill membranes free. 
 
 The opercular apparatus is complete, has a smooth margin a,nd its 
 angle is not spinous but sharp. Feather-like pseudobranchia are 
 present. The head has cavernous spaces in it filled with raucous, 
 much like that of the Gymnocephala of Europe (Jordan e.nd Evermann, 
 1896) . 
 
 There are two dorsal fins; the anterior has rays, the 
 
 posterior is an adipose fin. The anterior dorsal fin is supported 
 
 by two small spiny rays in front, and these are followed by nine j 
 
 to eleven soft articulated rays. The first spiny ray is about j 
 
 one-third, the second spiny ray about three-fourths the length of |j 
 
 the longest dorsal ray. Both spiny rays are firmer and somewhat | 
 
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 stiffer than the soft articulated rays. These spiny rays of Per- !| 
 copsis are much weaker than those spines commonly found in Acan- 
 thopterygian fishes. However, they show the characteristics of 
 true spines. The most anterior of the soft rays in the dorsal 
 fin differs from the other soft rays in this respect, it is long- 
 est and does not branch. The remaining soft rays divide twice 
 

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 dicho tomously before reaching the distal end. All of the soft j 
 
 rays are articulate. The fin is placed a little nearer the anter- 
 ior than the posterior end of the fish. The adipose fin is situated 
 
 I 
 
 I 
 
 midway between the anterior dorsal and the caudal fin. It is 
 small and lies close to the body. 
 
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 the sharp posterior angle of the suboperculum. Each has twelve 
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 anterior dorsal. Each has eight soft rays. 
 
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 at the distal end) support the anal fin. The spine is a little 
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 cle, strongly forked, long and slender. The caudal peduncle and 
 the caudal fin comprise almost two -fifths the length of the fish. 
 
 I 
 
 The measurements of a specimen of Percopsis guttatus I 
 
 is as follows: 
 
 Length of fish- - - - - - 
 Length of caudal peduncle 
 Length of caudal fin - - 
 Depth of caudal peduncle 
 Depth of body ------ 
 
 V/idth of body--- - - - 
 
 I 
 
 i 
 
 96 mm. (Caudal fin not included) 
 
 27 mm. 
 
 20 mm. 
 
 7 mm. 
 19 mm. 
 
 
 14 ram. 
 
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28 mm. 
 
 Length of head 
 Width of interorhital space - - - 6 mm. 
 
 Length of snout - -- -- -- --10 mm. 
 Length of maxillary - -- -- -- 7 mm. 
 Length of mandible - -- -- -- - 5 mm. 
 
 An excellent cut of P. guttatus may be found in 
 Agassiz ’’Lake Superior,” 1853. 
 
 III. Internal Anatomy 
 1. Alimentary System 
 
 (a) The mouth and pharyngeal region:- The mouth open- 
 ing is small. The p remaxi 1 lari es slightly protrude over the 
 dentaries. The teeth are small, villifotta, and more densely com- 
 pact together in the area nearest the juncture of the right and 
 left premaxillaries. On the dentaries the teeth are much more 
 numerous and more evenly distributed over the oral surface of 
 the bones. 
 
 Just posterior to the teeth are the two breathing 
 valves. They are membraneous organs, each semi-lunar in shape, 
 the upper and larger valve (maxillary valve) has the circular 
 edge attached to the inner margin of the premaxillaries, the 
 loose edge of the valve extending across from tlie base of one 
 premaxillary to the base of the other. The lower valve (man- 
 
- 7 - 
 
 dibular valve) is smaller, but is similarly attached to the den- 
 taries. 
 
 The dorsal part of the mouth arches rapidly posteriorly 
 for a short distance, then horizontally until it reaches the first 
 gill slit. The cavity formed by the arching narrows as it travels 
 backward because of the space taken up by the orbits, to again 
 broaden out until it reaches the first gill cleft. The epithelial 
 tissue has many minute longitudinal folds. There are no teeth in 
 this portion of the mouth, the surface being smooth to the touch. 
 The floor of the mouth anterior to the first gill cleft is less 
 deeply hollowed than the roof, but is toothless and smooth. 
 
 There is no true tongue. The copulae of the second, 
 third, and fourth branchial arches as well as the branchial arches 
 themselves bear very minute villiform teeth, all pointing backward. 
 Immediately back of the branchial arches the oesophagus begins. 
 
 The pharyngeal region of the roof of the mouth is marked off from 
 the anterior part by a deep and sha.rply defined transverse groove 
 at right angles to the longitudinal axis of the body. Just pos- 
 terior to this line are the plate-like superior pharyngeal bones. 
 There are three of these on each side of the median line and each 
 bear numerous teeth. The posterior margin of the last pharyngeal 
 bone marks the anterior margin of the oesophagus. 
 
 (b) The alimentary canal:- The alimentary canal, when 
 viewed from the exterior, consists of three well marked regions: 
 the oesophagus and stomach, the pyloric caecal region of the intes- 
 tine, and the simple intestine. The canal is siphonal, making two 
 distinct sharp bends in its entire length. Beginning at the 
 
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- 8 - 
 
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 pharyngeal region, it extends posteriorly to about one-half the 
 length of the body cavity where it suddenly turns toward the right, 
 and bending upon itself, extends anteriorly to the cardiac portion 
 of the stomach. There, suddenly turning dorsally, it again bends 
 upon itself and travels posteriorly to the end of the body cavity 
 where it opens to the exterior. The general linear outline of the 
 canal is that of a complete loop, the stomach having one bend, the 
 intestine one. Its whole length, however, the bends being drawn 
 out, will scarcely exceed 55 mm. and the canal when empty fills 
 about one- third the body cavity. 
 
 The oesophagus cannot readily be distinguished from the 
 stomach for the one gradually blends into the other. But the 
 greater part of the oesophagus has uniformity in shape that aids 
 in distinguishing it from the stomach. At the pharyngeal area it 
 is narrow, gradually dilating in the central portion of its length, 
 then restricts somewhat to again become broadened before it enters 
 the stomach. The inner membrane hangs in simple longitudinal 
 folds. The length of the oesophagus is normally about one-half 
 that of the stomach. 
 
 Brom its cardiac end, the stomach extends posteriorly 
 to about one-half the length of the coelom where it makes a sharp 
 bend toward the ri^t and then quickly ends in the pylorus. This 
 gives it a ”J*' shape with the long arm (cardiac portion) a large 
 distended sack; the smaller end (pyloric portion) being much 
 smaller, scarcely extending from the end of the large arm. Here 
 the pyloric valve is located. The abrupt bend of the stomach and 
 immediate ending in a pyloric valve gives no chance for the elonga- 
 

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- 9 - 
 
 tion of the posterior part of the stomach into a lar^e pocket so 
 characteristic of those Acanthopterygian fishes which Rathke 
 describes as inhabiting the fresh waters of Europe, the structure 
 which he calls the "Blindsack. •’ 
 
 The intestine begins at the pyloric end of the stomach: 
 first, as a dilated or enlarged tube in the region of the pyloric 
 caecae, then as a slender tube until it reaches the anus. The in- 
 testine is short (about twice the length of the stomach and oesoph- 
 agus combined) never coiled, and makes only one bend, forming a 
 loop, one arm of which is about three times the other, but the 
 shorter alone receives the pyloric caecae. The rectal portion 
 shows little differentiation, being only slightly larger in diam- 
 eter than the slender part of the tube. 
 
 Pyloric caecae are present in the section of the intes- 
 tine adjacent to the stomach. Their number varies between nine 
 and twelve in different individuals. These caecae are evenly 
 distributed in a linear arrangement on both sides of the intestine, 
 one row usually, thou^ not always, extending up to and enveloping 
 the left side of the stomach, the other is looped about the ven- 
 tral side. They are large, being about one- third the diameter of 
 the intestine and in length often reaching to about half that of 
 the stomach. Each has its individual opening into the intestine. 
 Within the area of this group of pyloric caecae the intestine 
 receives the bile duct. 
 
 There is a distinct constriction separating the stomach 
 from the intestine, ce.used by a band of circular muscles and con- 
 stitutes the pyloric phinxter. 
 

 
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- 10 - 
 
 The liver is very compact, closely packed in the anter- 
 ior part of the body cavity. It extends across the thorasic floor 
 of the cavity and well upon the sides covering completely the an- 
 terior cardiac part of the stomach as well as the "bend” of the 
 intestine. It has two lobes; the one containing the greater bulk 
 extends from the right side some distance into the left; the left 
 lobe is smaller but more marked in appearance. These lobes how- 
 ever are never very conspicuous, and at first si^t the liver 
 appears to be a compact triangle of tissue. The gall bladder, 
 though almost surrounded by liver tissue, is however distinct and 
 free from the liver and can be dissected out. The hepatic duct 
 enters the bladder in about the same position that the cholodocus 
 leaves it. The liver is extremely vascular. 
 
 Adjacent to the gall bladder and likewise imbedded in 
 the liver is the pancreas; an oblong structure with tv/o small 
 lobes at the posterior end due to a partial imprint of the gall 
 bladder pressing against its tissues. I was unable to determine 
 the exact course of the duct, but it seems to follow closely that 
 of the liver. The pancreas is very easily overlooked. 
 
 2. The Swim Bladder 
 
 I 
 
 The swim bladder of Percopsis lies outside of the deeply 
 pigmented peritoneum, dorsal to the alimentary tract and genital 
 orgains, and Just ventral to the kidneys. It extends almost the 
 whole length of the body cavity, being a little short of the ex- 
 treme anterior of the cavity, the result of the intervention of 
 
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- 11 - 
 
 I 
 
 the head kidneys which project ventrally from the dorsal wall. The 
 swim bladder is a simple sack, flattened dorso-ventrally. It grad- 
 ually narrows from the anterior end to the posterior until it 
 reaches about one-half the width it has toward the cephalic end. 
 
 On the anterior ventral surface is a large vascular and glandular 
 area (rete mirable) which extends over the anterior ventral surface 
 to about one-third the distance posteriorly and receives its arter- 
 ial blood from a branch of the coeliac axis, the venous blood leav- 
 ing it throu^ a branch of one of the mesenteric veins. These 
 blood vessels are supported by a mesentery which connects with the 
 alimentary canal, but there is no trace of a pneumatic duct in this 
 mesentery or in any part of the swim bladder. The whole bladder 
 can be dissected free from the body with no connection with the 
 alimentary canal save at the mesentery which bears the blood vessels 
 Gross dissection or cross sections do not reveal an open duct, or 
 any trace of an atrified duct. The swim bladder has no connection 
 with the head, being free from any structure of the head or anter- 
 ior vertebrae (i.e. no Weberian apparatus is present). 
 
 3. The Uro-Genital System 
 
 The nephridia of Percopsis are situated along the haemal 
 area of the coelom outside the peritoneum and dorsal to the swim 
 bladder. The two are separated from each other by the haemal ridge 
 of the vertebral column and are united to each other only at the 
 
 anterior end of the coelom in the region of the head kidneys. They 
 
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- 12 - 
 
 are divided into two divisions according to the kind of tissue 
 they contain. The large glandular area most anteriorly is the 
 pronephros (head kidney), the small long lohulated structure ex- 
 tending from the head kidney posteriorly is the mesonephros. 
 
 The head kidneys are large, lobulated, glandular masses 
 of tissue in the anterior part of the coelom and are united by a 
 narrow neck of like tissue. They suddenly grow smaller, becoming 
 differentiated into the long slender mesonephros. The mesonephros 
 can be described as a thin flat slender ribbon with the mesonephric 
 tissue situated in swellings, which accommodate themselves to the 
 hollow formed by the concavity of each vertebrae. The mesonephroi 
 continue posteriorly carrying the urinary ducts (which are imbedded 
 within the mesonephric tissue) with them until they reach the pos- 
 terior wall of the coelom. Here they follow the curvature of the 
 wall ventrally, and finally end into a small conical shaped bladder. 
 This bladder receives each of the two urinary ducts. It in turn 
 opens into the genital pore by means of a very short tube or duct. 
 
 Each kidney receives lateral renal arteries from the 
 dorsal aorta. They receive their venous blood from the ri^t and 
 left subcardinals, both of which arise from the caudal vein. These 
 veins and the post-cardinals run along the ventral surface of the 
 respective right and left kidney until the latter enter the sinus 
 venosus. The urinary ducts lie in the mass of kidney tissue near 
 the inner margin of the kidneys. 
 
 The gonads consist of two long oblong club-shaped sa.cs 
 united at the posterior end by a short large cylindrical duct that 
 terminates in a genite,! pore. ?.Tien at the hei^^t of sexual activity 
 
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-13- 
 
 the ovaries take up the larger part of the body cavity. They re- 
 ceive their arterial blood from a ri^^t and left genital artery; 
 the right of these being a branch of the artery that supplies the 
 rete inirable, the left from the left gastric artery. The genital 
 veins of the tv;o sides, so far as I could make out, are separs-te, 
 each emptying separately into the sinus venosus. Among all the 
 specimens dissected, I did not find any male. 
 
 4. The Nervous System 
 
 (a) The brain^:- The brain is very compact and larger 
 in proportion to the body than in most fishes. It lies in a 
 capacious cavity in the sku.ll entirely surrounded by a meninx 
 which fills the remainder of the brain case. The greatest v/idth 
 and depth of the brain is almost equal. In a specimen of P. gutta- 
 tus, 116 mm. long, the brain measured 5 mm. at its greatest v;idth 
 and depth, and 13.5 mm. in length (the olfactory extension not 
 included). With the olfactory tract included, the brain is about 
 18 mm. in length. 
 
 The rhinencephalon extends forward from the floor of the 
 telencephalon into a slender olfactory tract, the olfactory bulb 
 following the nares in their growth. Thus this tract is enlarged 
 into a bulbus olfactorus at the nares, so that the bulbus olfac- 
 torus v.'hich contains the olfactory nerve is some distance from the 
 telencephalon. The telencephalon is small, bilobed, each lobe 
 
 ^Condition of material at hand would not pemit detailed study of 
 cranial nervae. 
 

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-14- 
 
 conical in shape, and nearly the entire mass consists of corpus 
 striatum. The ventricles are almost obsolete for the thin pallial 
 tissue lies almost in contact v;ith the corpus striatum. 
 
 Ventral to, and entirely obscured from the dorsal as- 
 pect by the optic lobes is the diencephalon. In the anterior part 
 of the median ventral line is the large oval body, the infundibulum, 
 and just posterior to this the saccus vasculosus. I was unable 
 to remove the hypophysis from the base of the skull, so only the 
 scar was left on the ventral side of the infundibulum. On each 
 side of the infundibulum is the lobi inferiores. 
 
 The optic lobes (mesencephalon) are very large. They 
 extend anteriorly some^i^at over the posterior part of the telen- 
 cephalon and laterally somewhat on either side of the anterior 
 part of the metencephalon. The optic nerves pass anteriorly 
 and ventrally from the optic lobes on either side of the dien- 
 cephalon crossing each other just in front of the infundibulum. 
 
 This chiasma is peculiar in that there is a complicated inter- 
 lacing of bundles of fibres. I know of no other case among 
 Teleosts where as complicated an interlacing of fibres occurs. 
 
 The nearest approach to it is in Clupea harengus where the optic 
 nerve of the left eye passes throu^ that of the right^ that is, ^ 
 the nerve separates into two bundles and the nerve of the left 
 eye pa.sses throu^ this separation. (Gottsche, 1835). 
 
 Situated posteriorly in the dorso-median line and adja- 
 cent to the mesencephalon is the single lobed metencephalon (cere- 
 bellum). It is more elevated than the optic lobes and its mass 
 
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extends slightly between them. It has an ovoid conical shape. 
 
 The medulla oblongata (myelencephalon) is massive. It 
 extends anteriorly some distance beneath the optic lobes and pos- 
 teriorly to just behind the origin of the tenth nerve. Though 
 broad in front, it gradually tapers posteriorly and suddenly tapers 
 into the spinal cord. The fifth and seventh nerves ( trigeminalis 
 and facialis) have their origin in the anterior lateral aspect of 
 the myelencephalon. The eighth, ninth, and tenth nerves (acusticus, 
 glossopharyngeal, and vagus) follow in the order named along the 
 lateral margin of the myelencephalon. 
 
 IV. Discussion 
 
 Agassiz, 1653, was the first to describe Percopsis, and 
 throu^ him it bears the name it now has. The naked head, abdom- 
 inal ventral fins, and adipose fin he noticed as strikingly Salmon- 
 oid in type, yet the ctenoid scales, mouth, and spiny dorsal and 
 anal fins were exceedingly Percoid. His comment on the fish is 
 as follows: "Now my new genus Percopsis is just intermediate 
 
 between Ctenoids and Cycloids; it is what an ichthyologist at 
 present would scarcely think possible, a true intermediate type 
 between Percoids and Salmonidae.” To Agassiz the fish v/as dis- 
 tinctly an intermediate type betv/een two representative types of 
 Teleostian fishes, those of the Salmonidae and the Percidae. 
 
 In shape, one cannot say that the fish is distinctly 
 percoid or salmonoid. It is rather intermediate of the two. Its 
 greatest height is farther anteriorly than is usually marked in 
 

 
 
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-16- 
 
 the salmon, a characteristic which is percoid. However, the hody 
 is not so compressed as in the perches.^ 
 
 The external anatomy shows a great number of mixed char- 
 acters. The two spines of the anterior dorsal fin and the one of 
 the anal are characteristic of the Acanthopterygii . However, a 
 similar small fin, similarly placed, thou^ v/ithout spines, occurs 
 in both Cyprinidae and Salraonidae. Again a dorsal fin like that 
 of Percopsis exists among the pirate perches ( Aphredoderidae) , 
 v/hich are always classed as Aca,nthopterygians. The adipose fin 
 is purely a physostomous character which has been found only among 
 salmon-like fishes, and the Siluridae and a fev; deep sea forms of 
 the Haplomi. The species Columbia transmontana which Eigenmann 
 (l892) describes, perhaps helps to strengthen the claim that Per- 
 copsis is an Acanthopterygian. Though belonging to a different 
 genus, Eigenmann describes C. transmontana as undoubtedly of the 
 same family as Percopsis. It has two stiff strong spiny rays in 
 the dorsal and one or two in the anal fin. The scales on the an- 
 terior part of the body are more deeply ctenoid. Both Percopsis 
 and Columbia have the ventrals abdominal, which is distinctly char- 
 acteristic of isospondylous fishes. Their pectoral fins, however 
 are a little higher laterally than is usual in isospondylous fishes. 
 
 An Acanthopterygian fish of Europe, the Acerina or Gym- 
 no cephalous, which has a naked head with muciferous spaces in the 
 
 ^The specimens which I examined were at the height of sexual 
 activity, the ovaries greatly enlarged, the females being extreme- 
 ly full bellied. The fish at other times surely has not so large 
 a girth and more compressed than the specimens I' have now. 
 
 ll 
 

 
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-17- 
 
 skull resembles Percopsis in this respect (Jordan and Evermann , 
 1896). They (Jordan and Evermann) hint that this relationship 
 of Acerina and Percopsis “may be more than accidental." The pre- 
 maxillaries bearing the teeth and forming the entire upper margin 
 of the mouth is true of the Acanthopterygians and of the family 
 Ga didae. 
 
 Rathke (l837) gave the first extensive account of the 
 digestive tract of European fishes. He divides the alimentary 
 tract into three main divisions, the oesophagus, stomach, and 
 truncogaster or intestine. In most fishes the stomach is divided 
 in two regions, cardiac and pyloris. The intestine has a part 
 v;ith pyloric caeca and a longer tube reaching from the pyloric 
 caecal region to the anus. The pars pyloric of the stomach is 
 often drawTi out in a more or less elongated sac which he calls 
 the "blind sac." Thus the intestine arises not from the extreme 
 posterior end of the pyloric part of the stomach, but more or 
 less toward the middle, the length and width of the blind sac 
 being roughly proportional to the length and width of the body 
 cavity. The blind sac predominates in the Acanthopterygii. Per- 
 copsis has no blind sac and in this respect it differs from the 
 Ac an thop terygian type. The canal of Percopsis does resemble that 
 of Mullus ba.rbatus in respect to the appendices pyloricae which 
 are in small number and distributed evenly on the right and left 
 side of the intestine, but the intestine of M. barbatus differs 
 from Percopsis in its being longer and making tv/o bends instead 
 of one before it reaches the exterior. The stomach, too, is short 
 
jH*.. ' 
 
 
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-18- 
 
 like that of Percopsis tut differs from Percopsis in that it has 
 a sme.ll tlind sac. 
 
 Jacotshagen (1912) has putlished on the alimentary tract 
 of fishes. Besides his own individual work, he quotes from many 
 of his predecessors and contemporaries. He notes that in many of 
 the genera of the Salmonidae, especially the genus Salmo, there 
 is no tlind sac (except in Salmo autumnalis) and the numter of 
 pyloric appendages is very variatle, from 288 in S. unimaculatus 
 to 20 in S. hoodii. The appendages, however, are arranged in 
 
 I 
 
 equal numter in a linear series on the rigjit and left side of the 
 intestine. The canal is siphonal, a double tent tube, the stomach 
 receiving one tend, the intestine one; the shorter aim of the 
 intestine receiving the pyloric appendages. The canal of salmo 
 then is very like that of Percopsis if the numter of pyloric appen 
 dages were reduced. 
 
 The simple swim bladder v/ith no connection with the 
 alimentary tract places Percopsis outside the pale of physostomous 
 fishes. It has always heretofore teen described as being physos- 
 tomous. Gunther ( 1866) says that it probably has a pneumatic 
 duct. He placed it in his order Physostorai and gave it a place 
 just after his family Salmonidae Vvith the family name of Percop- 
 sidae. Jordan and Evermann (l896) say that the "air bladder is 
 present with a band of connective tissue v/hich is apparently with 
 a- rudimentary duct." They place it among the very first of the 
 Ac an thopterygian fishes making a sub-order Salmopercae of it. 
 Kingsley (1899) does the same. Browntree (l903) dissected a large 
 
V 
 
 V \ 
 
_1Q_ 
 
 JL w 
 
 1 ' 
 j 
 
 i 
 
 1 
 
 i 
 
 number of supposedly physostomous fishes of different families and | 
 genera to determine the position of the pneumatic ducts. Among | 
 
 these fishes which he dissected were two specimens of Percopsis j 
 
 guttatus and one of Columbia transmontana. He says that they are I 
 
 I 
 
 physostomous and that the pneumatic duct opens to the right side 
 of the oesophagus. Boulenger (1904) claims P. guttatus to be phy- 
 sostomous but places it among the Haplomi because of skeletal struc- 
 tures. Goodrich also claims for it a pneumatic duct, but like Jor- 
 dan and Evermann, gives it a place as lowest of the Acanthoptery- 
 gians. 
 
 I have made sections of the place where the duct should 
 be, and I find that there is no duct present, either open or atro- 
 phied, between the alimentary canal and the swim bladder of Peroop- 
 sis. My observations agree with those of Regan (1909 and 1911), 
 who says, "The Salmopercae are physoolystlc; I cannot find any 
 trace of a pneumatic duct. In this I am confirmed by Dr. W. G. 
 Ridewood, who kindly examined an example of Columbia transmontana." 
 Thus Percopsis is not a physostomous fish and cannot be classed as 
 such upon the basis of the swim bladder. The simple ductless sac- 
 like bladder is mors like that found in the Acanthoptsrygii . 
 
 The brain of Percopsis in external appearance resembles 
 that of the salmon and perches as to relative size of optic lobes, 
 cerebrum and medulla oblongata. It differs materially from the 
 Salmonidae in that the csrebsllVJm is not so large as that of the 
 Salmonidae; not extending far back on the myelencephalon j < 
 
 and that in the Percopsidae the olfactory lobes are directly 
 
- 20 - 
 
 oonnected to the nasal sacs being united to the telencephalon 
 
 by an olfactory tract (tractus olfactorus), while in the salmon 
 
 the olfactory lobes are adjacent to the telencephalon, separated 
 
 only by a shallow circumscribed groove and the olfactory nerves 
 
 greatly elongated. The olfactory lobes and nerves of Percopsie 
 
 are like those of the salmon and trout except the external struc- 
 
 which 
 
 ture of the brain of Percopsi^does not differ from that of per- 
 ches. 
 
 The position of the olfactory lobes in Percopsis is 
 comparable to that found in those physostomous fishes included 
 in the Siluridae, Cyprinidae and of those Isoapondylous fishes 
 of the family Hyodontidae. According to Herrick (1891) these 
 fishes all have a long olfactory tract with olfactory bulb adja- 
 cent to the nasal sacs. This condition of nasal organs to olfac- 
 tory nerve is also found in the Gadidae (Goodrich 1908). Of 
 these fishes which Herrick describes, the brain of Hyodon tumidus, 
 though longer and less compact, is most comparable to that of 
 Percopsis. 
 
 Stannius (1854) mentions 28 families and genera of Tele- 
 ostean fishes which had been investigated up to his time.^ These 
 
 So bei alien bisher untersuchten Percoi'den, Cataphracten, Scidn- 
 ofden, Sparoi’den, Mugiloi'den, Squamipennen, Scombero3!den, Tdni- 
 ofden, Thentyern, Blennioi'den, Gobiofden, Clycopoden, Pediculaten, 
 Labrofden, Chromiden, Scomber-Esoces, Pleuronectiden, Fistulares, 
 Esocinen, Salmoniden, Clupefden, Murdnofden, Gymnotini, Lopho- 
 branchii, PlectognathiT-Oadofdei , Siluroi'dei, Cyprinoldei . 
 
r^'’’ • ;*• . i- v*v ..•■„-*■! . . -’.V . : i' 
 
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 •'’’’ ‘ - . ■ V- -, ■ V' , •<,. >-* 
 
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- 21 - 
 
 inoluded a wide range of fishes both physostomous and physoclia- 
 tous fishes. All have olfactory lobes attached directly to the 
 telencephalon except those families of the Gadofdea, SiluroSdea, 
 and Cyprinoldea. The Siluridae and Cyprinidae are classed as low 
 type fishes, yet the Anacanthini, of which the Gadidae is a family, 
 are one of the highest types. The former type - the long olfactory 
 nerve - seems to predominate, so it is hard to say which condi- 
 tion is most primitive. From general structure it is not possible 
 that Percopsis is as high a type as the cod. One thing is certain: 
 the brain has mixed characteristics, but resembles the type of 
 brain found in the Percidae, Hyondontidae and Gadidae. 
 
 V. Conclusion 
 
 To determine the position of Percopsis guttatus by ana- 
 tomical structure other than skeletal is not easy. The naked head; 
 small adipose fin; the small anterior dorsal fin of soft articu- 
 lated branched rays; the ventral fins almost abdominal in posi- 
 tion; and the slphonal alimentary canal with its linear arrange- 
 ment of pyloric caecae, but with no blind sac; show decided 
 Isospondylous characteristics. On the other hand, it is just as 
 strikingly Aoanthopt erygian for there is present two true dorsal 
 fin spines; one anal spine, the premaxi liar ies form the margin 
 of the jaws and bear teeth; the scales are ctenoid; the body 
 is perch-like in shape, and the swim bladder is entirely ductless. 
 
 In respect to the olfactory region, the brain is the 
 
. .--.w 
 
 '-' ■ 4 £ ' V- ' a ‘ ■ A ’i- ' ’4--' 
 
 ^ ^ 
 
 
 ir- 
 
 5fca 
 
 '''* * *■'■ ^ 4 «'* ***/ I A •‘^' ( " ' 'i^ 
 
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 vri,: V ■' ■ ■■. ' ;■ .Silifi. ,|1^' ^ 
 
 
 ^ 1 
 
 fi.. 
 
- 32 - 
 
 type that belongs to the more primitive fishes, suoh as the Cyprln- 
 idae or Siluridae. In these fishes the olfactory bulbs are ;)oined 
 to the nasal sacs and are connected to the telencephalon by a long 
 olfactory tract. In this respect Percopsis guttatus is primitive. 
 But even the resemblance of the brain of Percopsis to the Siluri- 
 dae and C^^’prinidae does not prove that it belongs to the Ostario- 
 physi, for the Weberian apparatus which predominates in these 
 forms is not present in Percopsis. 
 
 If the skeletal structures are excluded, the greatest 
 amount of evidence tends to show that the Percopsidae are primi- 
 tive Acanthoptsrygians. The perooid mouth, fin spines, and duct- 
 less air bladder having the most weight in favor of the Acanthop- 
 terygii. The Percopsidae seem to have arisen from those types of 
 fishes which were Isospondylous in regard to external structure 
 and viscera, but retained the brain structure of the Eventognathi . 
 The Percopsidae are transitional forms, having entered the thres- 
 hold of the Aoanthopterygii , but never developing farther, have 
 retained some archaic features. 
 

 5 i^, 
 
 
 '■: 'v ■ '. n. . ^ ' 
 
 tg ’i'iMfi* •’' •* ■■ *' ■ ■■ ■•*. f.' >•% i ■#. y 
 
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 'j ""‘- ■••.'' I • ' ft “. * “H<- •'’*'■ f ^ 
 
 
 
 t'- ^rr.‘,-rr' ' »'jsK-^- .A eio:^ «is;ji"%ifi|^T 
 
 4 
 
 .v;-. ■- ; 'v\ , •■-“•■■ i:- ' . '’'^' ■^$' 2 . 
 
 *'itr’ .CJ2»it»«ifx«. 1 kj; #;o.|;\ '\- ip^ 
 
 V 1 J t. / A tiv- ' ^a: fcV*<koe|\lSirjfe 
 
 
 ^'r-- ' 7 “"‘’'-*'- • '■ " 
 
 ^.1 ■•_ S&if'*-' Va^SfAi'r .:^«j .r. ’ ’A, >4! ■» •.’ ; ^ d..iU ' . X' ':a-L l-\ 
 
 ii> . - ■ . i-i-.j * > I-'.-. " •. •J.-,‘x ' .H.,i 
 
 |;^;" ' ..-A/.:;:. 
 
 
 
 
 ^ 'r%]y,'y.'i.^ vs.. 
 
 riJi. : ^jr.ii' 
 
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-23- 
 
 VI. Bibliography 
 
 Though all the authors mentioned in this bibliography 
 have not been mentioned in this text, their work has been con- 
 sulted and the contents in respect to the subject matter pertain- 
 ing to this paper have been noted. 
 
 Agassiz, Louis 
 
 1850 Lake Superior, pp. 384-289. 
 
 Boulenger, George Albert 
 
 1904 A Synopsis of the Suborders and Families of Telsos- 
 tean Fishes. Annals and Magazine of Natural History. 
 Vol. 13: 161-190. 
 
 Boulenger, George Albert 
 
 1904 Teleostei (Systematic Part). The Cambridge Natural 
 History. Vol. 7. 
 
 Browntree, Walter S. 
 
 1903 On some Points in the Visceral Anatomy of the Chara- 
 oinidae, with an Enquiry into the Relations of the 
 Ductus pneumaticus in the Physostomi generally. Trans. 
 Linnean Society of London, pp. 47-61. 
 
 Dahlgren, Ulric 
 
 1898 The Maxillary and Mandibular Breathing Valves of 
 
 Teleost Fishes. Zoological Bulletin, Vol. 2: 117-124. 
 Dean, Bashford 
 
 1895 Fishes, Living and Fossil. 
 

 ■ * 
 
 \r ,' ■ ' ‘ 
 
 j -nai! 
 
 
 >»> M 
 
 :[ttov^ 4fS£fp;f ^7X&^ 
 
 ■; ■« ■,.. . ’. v! 1 d ^ - ■'• '■ ?•■ :'v‘? I :tv 
 
 ■V. .-a:- !». : r- VIS'’: -)*^;. '*w • *. 
 
 »/■ 
 
 
 tjE'^Jgl'i .T • - 
 
 ‘7ijOO;+>T £ 
 
 ,v.l« 
 
 'r-rJ 
 
 ■■'• » '"' 1^ ’ ' ■■’ ■ •■'■ & ' FT? 
 
 TvMc'tSE ■‘?J',fltS'-*6.;«^W4r A ■ ♦«&*• ■»n'^*a*' 
 
 ' ' ir!^>'^ 
 
 v‘' ' m'^ 
 
 .m ;!'S«i 
 
 *f>’ 
 
 . . . '., ^-A .:;■ -T : ‘K.», m 
 
 ' ^ ' v''// ;^,. 
 
 
 
 
 i*' ■"' li • * & 
 
 »;«xag; tfiaj : a5)r : s 
 
 * .^y^'ldf* r S ■*_ , . t 5-^ ■* B 
 
-24- 
 
 Eigenmann, Carl H. 
 
 1893 The Percopsidae of the Pacific Slope. Science, 
 
 October 21, pp. 233-234. 
 
 Gegenbauer, Carl 
 
 1898 Vergluchende Anatomie der Wirbelthiere . Band 1. 
 
 Goodrich, E, 6. 
 
 1909 Vertebrata Craniata (First Fascicle: Clyclostomes 
 and Fishes) in "A Treatise of Zoology” edited by 
 E. Ray Rankest er. Part IX. 
 
 Got t ache, G. M, 
 
 1835 Vergluchende Anatomie des Gehirns des Grdtenf ische, 
 Reichert Archiv, pp. 244-294; 433-486. 
 
 Gdnther, Dr. Albert 
 
 1859 A Catalogue of Aoanthopterygean Fishes. Vol. 1-8. 
 
 Gdnther, Dr. Albert 
 
 1880 An Introduction to the Study of Fishes. 
 
 Eerrick, C. L. and C. Judson 
 
 1691 Contribution to the Morphology of the Brain of Bony 
 Fishes. Journal of Comparative Neurology. Vol. 1: 
 311-245. 
 
 Jacob Shagen, Dr. Edward 
 
 1912 Enter suchungen iiber das Darmsystem der Fische und 
 
 Dipnoer. Jenaische Zeitschrift ftlr Naturwissenschaf t . 
 Teil II Material, zur vergluoh. Anat . des Darmkanal 
 der Teleostomen - pp. 373-810. 
 

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-25- 
 
 Jordan, David Starr, and Evermann, B. W. 
 
 1896 The Fishes of North and Middle America. Bui. U. S. 
 
 Nat . Museum . 
 
 Jordan, David Starr 
 
 1905 Guide to the Study of Fishes. 
 
 Maoallum, A. B. 
 
 1884 Alimentary Canal, Liver, Pancreas, and Air Bladder of 
 Amiurus catus. Proo. Can. Inst. Toronto. 
 
 Oppel, Albert, Dr. Med. 
 
 1896-1913 Lehrbuoh der vergleichenden mikroskopichen 
 Anatomie der Wirbelthiere . Jena. 
 
 Parker, Thomas Jeffrey 
 
 1884 A Course of Instruction in Zootomy, pp. 86-129. 
 
 Rathke, Heinrich 
 
 1837 Zur Anatomie der Fische. Reichert Archiv. Part II 
 pp. 305-356. Hierzu Taf. XVII - XIX. 
 
 Regan, C. Tate 
 
 1909 The Classification of Teleostean Fishes. Ann. and 
 Mag. Nat. Hist. Vol. 3: 75-86. 
 
 Regan, C. Tate 
 
 1911 Anatomy and Classification of Teleostean Fishes of the 
 Order Salmopsrcae. Ann. and Mag. Nat. Hist. Vol. 7. 
 Stannius, Herman 
 
 1854 Handbuch der Anatomie der Wirbelthiere. Vol. 2, 
 
 Vogt, Carl, und Yung, Emil 
 
 1885 Lehrbuch der Praktischen Vergleichenden Anatomie. 
 Zweite Bund, pp. 470-543. 
 

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PLATE I 
 
 1. Brain (ventral view) 
 
 2. Brain (lateral view) 
 
 3. Brain (dorsal view) 
 
 cer. 
 
 - 
 
 - 
 
 - - cerebrum 
 
 cert. 
 
 
 - 
 
 - - cerebellum 
 
 CO. 
 
 - 
 
 - 
 
 - - optic chiasraa 
 
 hyp. 
 
 - 
 
 - 
 
 - - hypophysis 
 
 inf. 
 
 - 
 
 - 
 
 - - infundibulum 
 
 li. 
 
 - 
 
 - 
 
 - - lobi inferiores 
 
 med. 
 
 - 
 
 - 
 
 - - medulla oblongata 
 
 0 II 
 
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 - 
 
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 ol. 
 
 - 
 
 - 
 
 - - olfactory lobe 
 
 olt. 
 
 - 
 
 - 
 
 - - olfactory tract 
 
 opt. 
 
 1, 
 
 
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 V. 
 
 - 
 
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 VI. 
 
 - 
 
 Nervus abduscens 
 
 VII. 
 
 - 
 
 Nervus facialis 
 
 VIII. 
 
 - 
 
 Nervus acusticus 
 
 IX. 
 
 - 
 
 Glossopharyn geal 
 
 X. 
 
 - 
 
 Vagus 
 
 4. Alimentary Tract 
 
 an. - - - - anus 
 
 cd. - - - - cardiac (stomach) 
 
 in. - - - - intestine 
 
 li. - - - - liver 
 
 oe. - - - - oesophagus 
 
 pyl.- - - - pyloric (stomach) 
 
 pylc. - - - pyloric caecae 
 
 sp. - - - - spleen 
 
 5. Stomach 
 
 6. Swim Bladder (ventral view) 
 
 7. Swim Bladder (lateral view) 
 
 ret. - - - rete mirahle 
 art. - - - artery 
 
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The work of this paper was carried on in the Zoological 
 
 Laboratories of 
 of Professor J. 
 cere thanks for 
 
 the University of Illinois, under the direction 
 S. Kingsley, to whom the writer extends his sin 
 his guidance and helpful suggestions. 
 
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