78 THE LIMITS OF THE CLASS OF FISHES. 
any contiguous classes in the entire animal kingdom ;* that, further- 
more, they are significant of the highest class taxonomic value is 
indicated by their fundamental nature, and the coérdination of 
all parts of the organization. 
„There is also no longer reason for hesitancy in the admission of 
such a rank on the plea of imperfect knowledge of structure or 
the supposition that it may be the young of some other form f—_ 
a suspicion formerly common to many and shared by the author. 
With these facts, therefore, something more than mere assertion 
of opinion is requisite before the title of the group to at least 
class rank can be questioned. 
A much mooted question has been what are the characters of - 
the class of fishes, and how are they distinguished from the class 
of batracbians. This question has been discussed by Dr. Brandt, 
of St. Petersburgh, in an elaborate memoir. So long as the 
fishes, Marsipobranchiates and Leptocardians, were confouniled 
in one class, the extreme variations of the so-called class 
blinded one to the minor differences that would otherwise have 
been seized, and the result was that no absolute characters were 
discovered to limit the so-called class. But the class purged of 
the Marsipobranchiates and Leptocardians offers no longer such 
obstacles, and although the characters appear to have been over- 
looked hitherto, it is not the less true that all the known fishes are 
absolutely distinguished from all the known batrachians by very 
* PARKER (William Po “On th Development of the Skull of the 
Common Frog (Rana tempora sepa Tr. 1871, p. 202-3], well remarks “The 
btaa existing apa rier en is rte Myxinoid (lamprey, hag, Bdellostoma); between 
and the lowes e, the lancelet (Amphioxus), there is a gap, the extent of 
whi b itself is not anere the 
boundary form... .. pi anatomist will at once see that a creature igher in 
type than the unhatched embryo of the frog is yet an untold distance fi Pa of 
the lancelet which yet is only the known lowest of the great vertebrate subkingdom. 
t BERT (P. ) Sur PAmphioxus. Notede M. P. Bert... .. <Comptes rendus 
hebdomadaires des séances de Académie des Fen agda t. 65, 1871, pp. 364-7; 
translated (On the anatomy and physiology of Amphioxu ei a and Mogn 
zine of Natural History, third series, 20, 1867, Se . 302. Contains notes on the ejection 
of semen, etc. : 
KOWALEVSKY (A. i ic} tus. 
. 1857. [4to. 1 pl., 17 pp. tpi) < $ Mémoires « de PAcademié annara des Sciences 
, viie 
á 
-Piler bo 
_ An account of the development et tis ijas: The eggs are expelled through the 
i BEANDT (Johann Friedrich. Bemerkungen tiber die perpen dar Kalininiigoii ; 
Riickenmarkthier ortung der Frage Was ist ein Fisch 
de PAcadémie Impériale oe ae 
