PERCH. 



27 



I'erca italica, Cuv., Vai.., 1. c, ]i. 45. 



Bodiamis flavescens, Mitschim,, Trniis. Soc. N. York, I, p. 421; 



Cuv., Vai.. (Perca), 1. c, p. 46 ; Stelndachner, Sitzber. 



Akad. Wiss. Wion, LXXVIII, Abtli. 1, p. .399. 

 Perca serratu-i/niniiliita, J', i/nniiilata, P. acuta, P. gracilis, 



Cuv., Val., 1. c, pp. 47 — ^.00. 



Perca americaita, Schrank, Gii.l; vide Jorp. et Gii,b., <Sy7i. 

 Fis/i, A'. Amer.. 1. c, p. 524. 



Obs. GUnther", Steindaciiner'' and Day'' liavc nil tliree stated 

 that the North American Perca flavesvens, which is spread over the 

 east of the United States and Canada, should be reckoned as a variety 

 of the same species as the European perch. This opinion has, liow- 

 ever, been subsequently contradicted most flatly by Jordan and Gii,- 

 DERT''. Most of the characters given by the last-named authors as 

 distinguishing between the two supposed species, have already been 

 disproved by Day (1880), who pointed out the want of uniformity in 

 the American perches with regard to tlie length of the head, the 

 roughness of the body, the stripes, the spines of the bones, the num- 

 ber of the fin rays and of the rows of scales. However, Jordan and 

 Gilbert (1882) adduce, as a foumlation for this distinction of species, 

 some further circumstances^, to investigate the trutli of which we have 

 examined 4 specimens which we have received through the Smithsonian 

 Institution. Two of these specimens are from the Potomac and about 

 190 mm. in length; the third from Pekin in Illinois, and 183 mm. 

 in length, and the fourtli from Connecticut River, and 118 mm. in 

 length. On comparing these specimens with each other and with Euro- 

 pean specimens, we found that the most modern evidence to prove 

 a difference of species is also untenable. In the European perch, it 

 is true, the scales are smaller and the iirst dorsal fin begins more 

 forward than in the American. The latter point is shown most clearly 

 by the fact that in the European perch a row of scales from the be- 

 ginning of this fin downwards in an oblique, forward direction, gene- 

 rally meets the lateral line at the first scale, and contains 8 or 9 

 scales, while in the American variety it generally meets the lateral 

 line at the third or fourth scale, and contains 5 or 6 scales. In one 

 of the specimens from the Potomac, however, the line contains 8 scales, 

 and meets the lateral line at the first scale. In these American spe- 

 cimens the gill-rakers are not a bit broader than in the European perch 

 of the same size. In the smallest specimen from America the pseudo- 

 branchi.T resemble true gills as closely as in the European perch, but 



in the larger ones they are covered (»glandulou8»), a peculiarity which 

 may also be observed in older specimens of the European perch. Thus, 

 no difference of species has yet been proved between the European 

 perch and the American. However, tlie wide geographical separation 

 which has so long existed, has not failed here, as well as in other 

 similar cases, to leave traces of the influence of the different natural 

 environments on the form of the fish. The European perch lias gene- 

 rally a greater number of spinous rays in the first dorsal fin, and the 

 base of this fin is generally longer in the European perch than in the 

 American. The length of the base in proportion to the, length of the 

 body increases with age, so that in the European perch about 200 mm. 

 in length the base of this fin is on an average, according to measure- 

 ments taken from newly-caught specimens, 32.9 % of the length of 

 the body, wliile the corresponding average proportion in the European 

 perch from 260 to 330 mm. in length, is 34.5 %. In the four spe- 

 cimens of the American perch.'' mentioned above, which are preserved 

 in spirits, the corresponding average is 28 %, while in still smaller 

 specimens of the European perch, also preserved in spirits, and from 

 106 to 109 mm. in length, it is 29.7 fo. In the smallest European 

 perch that we have measured, 36'/2 mm. in length, the proportion 

 was 26 %. The tendency of these changes due to age shows that 

 the European type is more highly developed than the American. The 

 least depth of the tail too is proportionally greater in the American 

 perch, and also in younger specimens in contradistinction to older 

 ones"; but the length of the base of the anal fin in proportion to the 

 lengtli of the body, seems, on the contrary, to diminish with age, and 

 is less in the American type than in the European*. This contrast 

 in the course of development among these fishes, to judge by the 

 specimens before us, causes a radical difference, which is most clearly 

 shown by the fact that the least depth of the tail is less than 75 % of 

 the base of the anal fin in the European perch, while in the American 

 it is at least 93 "o. We should be compelled to acknowledge that 

 so important a character constitutes a difference in species, but for 

 the fact that it does not hold good in abnormal specimens of the 

 European perch, e. g. the so-called Carass Perch. Tlie great simila- 

 rity in various respects between Perca fluviatilis and P. americana, 

 which has already been proved by the authors quoted above, renders 

 it most natural to regard these forms as varieties of the same spe- 

 cies, which, during a geographical separation of long duration, have 

 deviated in certain respects from each other's course of deve- 

 lopment. 



" Uat., 1. c. p. 50. 



'' Sitzber., 1. c. Cf. also Proc. U. S. Nat. Mus., vol. I, p. 243. 



' Fixh.. 1. c. 



<' Syn., 1. c. 



' "The most important characters, the difl'erencc in the insertion of the dorsal, and in the gill-rakers and pseudobranchise, have not 

 been noticed by those writers who have decided that our species is identical with the European.'" 



•'' With regard to the character given by Jordan and Gilbert, that in the American perch the first spinous rays in the anterior dorsal 

 fin are shorter than the corresponding rays in P. fluviatilis, we may state the difference in this respect between the two specimens from the 

 Potomac, which are almost equal in size. In one of these specimens the first spinous ray is about half as long as the second, which in its 

 turn is about '■'/j of the third in length. In the other specimen the length of the first ray in proportion to the second is about the same 

 as that of the second to the third in the first-mentioned specimen. The latter too has 14 spin<ms rays in the first dorsal fin, while the second 

 specimen has only 13, i. e. the first spinous ray is wanting. Again, the first specimen has a black patch on the anterior and also on the 

 posterior portion of the first dorsal fin, while in the second these spots are absent. 



■' In the European perch we have found the least depth of the tail in specimens 36' o mm. in length and preserved in spirits to be 

 27 «<, of the length of the head, in newly-caught speciiuens on an average 210 mm. in length, 25.8 %, and in newly-caught specimens on 

 an average 291 mm. in length 24.1 %. The minimum proportion thus found was 23.8, tlie maximum 27. In the American specimens men- 

 tioned above, which are preserved in spirits, and on an average 169 mm. in length, the least depth of the tail is on an average 29.9 % of 

 the length of the head, the minimum being 29.3 °i, the maximum 30.6 %. 



'• In the European variety the base of the anal fin is more than, equal to, or only a little less than 10 'i of the length of the body : 

 in 13 measured specimens it turned out to be at least 9.4 %. In the .\merican specimens mentioned above it is at most 8.6 ". of the length 

 of the body. The number of rays in tliis fin varies also in these specimens between - g and - ,. 



