PERCH. 
27 
Perea italica, Cuv., Val., 1 . c., p. 45. 
Bodianus flavescens , Mitschill, Trans. Soc. N. York, I, p. 421; 
Cuv., Vat,. (Perea), 1. c., p. 46; Steindachner, Sitzber. 
Akad. Wiss. Wien, LXXVIII, Abth. 1, p. 399. 
Perea serrato-granulata, P. gramdata, P. acvta, P. gracilis , 
Cuv., Val., 1. c., pp. 47 — 50. 
Perea americana, Schrank, Gill; vide Jord. et Gilb., Syn. 
Fish, N. Amer., I. c., p. 524. 
Obs. Gunther 0 , Steindachner * 6 * * 9 and Day c have all three stated 
that the North American Perea flavescens, 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, how- 
ever, been subsequently contradicted most flatly by Jordan and Gil- 
BERT d . 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 the 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 foundation for this distinction of species, 
some further circumstances e , to investigate the truth 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 fourth 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 first 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- 
branchiae resemble true gills as closely as in the European perch, but 
in the larger ones they are covered (»glandulous»), a peculiarity which 
may also be observed in older specimens of the European perch. Thus, 
no difference of species has yet beeu proved between the European 
perch and the American. However, the 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 has 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, while 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 perchJ 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 %. In the smallest European 
perch that we have measured, 36 '/a 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 
onesS'; but the length of the base of the anal fin in proportion to the 
length of the body, seems, on the contrary, to diminish with age, and 
is less in the American type than in the European 6 . 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 %. 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. The great simila- 
rity in various respects between Perea 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. 
0 Cat., 1. c. p. 50. 
6 Sitzber., 1. c. Cf. also Proc. U. S. Nat. Mus., vol. I, p. 243. 
c Fish., 1. c. 
d Syn., 1. c. 
e “The most important characters, the difference in the insertion of the dorsal, and in the gill-rakers and pseudobranchite, have not 
been noticed by those writers who have decided that our species is identical with the European.” 
f 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 2 /, 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 spinous 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 abseut. 
9 In the European perch we have found the least depth of the tail in specimens 36.'/ 2 mm. in length and preserved in spirits to be 
27 % of the length of the head, in newly-caught specimens 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, the 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 °/, the maximum 30.6 %. 
6 In the European variety the base of the anal fin is more than, equal to, or only a little less than 10 % of the length of the body: 
in 13 measured specimens it turned out to be at least 9.4 °/o. In the American specimens mentioned above it is at most 8.6 % of the length 
of the body. The number of rays in this fin varies also in these specimens between 2 / fi and 2 / s . 
