Decembeb 23, 1910] 



SCIENCE 



926 



ered, he regards the demand for an ahnost dia- 

 metrically opposed tjT)e of presentation as 

 justified. None the less, he is grateful for the 

 availability of so admirable a text, written 

 under so different an inspiration. The stu- 

 dent with a fair foothold on the subject will 

 here find the means of strengthening his 

 grasp upon the problems arising specifically 

 from the experimental issues. 



Joseph Jasteow 



V' 



LOVIS AOGASIZ'8 LATER VIEWS ON THE 

 CLASSIFICATION OF FISBES 



Writers on ichthyology have expressed two 

 distinct views concerning Louis Agassiz's 

 work on the fishes. On the one hand, they 

 have praised his contributions to descriptive 

 ichthyology and his masterly work on the fos- 

 sil forms; on the other, they have condemned 

 his classification — declaring that a system 

 which rests solely upon differences in scales is 

 superficial and unphilosophical, and, even for 

 his day, was a step backward, rather than for- 

 ward. 



But in thus condemning Louis Agassiz's 

 views an injustice is done him, for he is 

 credited only with the classification he elab- 

 orated early in life (in his "Poissons Fossiles," 

 1833-1844:), but later abandoned and, in fact, 

 repudiated. No cognizance is taken of his 

 maturer views expressed many years later, at 

 a time when he had ceased to contribute in 

 any marked degree to the descriptive side of 

 his science. One reason for this neglect of his 

 later views is the fact that they were not 

 elaborated in detail, but presented in bare 

 outline before various societies; and are scat- 

 tered in a dozen or two paragraphs through 

 the proceedings of these societies. It is worth 

 while, it seems to the writer, to bring together 

 these later views of Agassiz and to indicate 

 the steps by which he arrived at them. 



As is well known, Louis Agassiz's larger 

 works on the fishes were published in Europe. 

 After coming to America he occupied himself 

 chiefly with the invertebrates. None the less 

 he never lost sight of his favorite group and 

 continued his observations in it whenever op- 

 portunity offered. But he worked at so many 



subjects and with such haste that he never 

 found time to elaborate all these observations. 

 Except for three or four short papers' in 

 which results were presented in more or less 

 detail, his views on the fishes were set forth 

 briefly. In the Proceedings of the American 

 Academy of Arts and Sciences, and of the 

 Boston Society of Natural History, during the 

 fifties and sixties, are scattered numerous con- 

 densed records of his observations, some of 

 great interest. 



His earliest allusion to his first classifica- 

 tion is found in a communication which he 

 made in 1850* to the American Academy of 

 Arts and' Sciences, on the scales of the bonito. 

 He showed that these scales are intermediate 

 between the ctenoid and the cycloid types, the 

 serrations being marginal only and not tra- 

 versing the whole posterior portion of the 

 scale. 



In 1857^ he announced that he had given up 

 the classification of fishes by their scales 

 and proposed a new classification which he 

 said was founded upon embryological char- 

 acters — although he did not specify what these 

 characters were. He divided the fishes into 

 four classes: (1) Selachians, (2) ganoids, (3) 

 fishes proper, (4) myzonts [^ cyclostomes]. 



This system, if we allow for the changes 

 wrought since Agassiz's day in the group of 

 the ganoids, is not much different from our 

 modern ones. In ranking his groups as 

 classes he was ahead of his time. There is a 

 tendency at the present day to make the Cyclo- 

 stomes and the Selachians, classes,* equivalent 

 in rank to the class Pisces proper. Such a 

 view, for instance, has recently been urged by 

 Gill and, as far as the Selachians alone are 



' A surcmary of these is given by Jordan in his 

 "Agassiz on Recent Fishes," in the American. Nat- 

 uralist, XXXII., 1S98, pp. 173-17C. 



■Proceedings, II., p. 238. 



'Proceedings Academy Arts and Sciences, IV., 

 pp. 8-9. 



' It does not appear that Louis Agassiz used the 

 word class with precisely the same connotation as 

 given to it to-day. It was then used somewhat 

 more loosely. However, this does not depreciate 

 the value of his conclusion that these four groups 

 are of equivalent rank. 



