VI.] SPECIES AND TIME. 159 



highly organized sharks and rays) and the Ganoids, a 

 group now poorly represented, but for which the sturgeon 

 may stand as a type, and which in many important re- 

 spects more nearly resemble higher Vertebrata than do the 

 ordinary or osseous fishes. Fishes in wdiich the ventral 

 fins are placed in front of the pectoral ones {i.e. jugular 

 fishes) have been generally considered to be comparatively 

 modern forms. But Professor Huxley has obligingly in- 

 formed the author that he has discovered a jugular fish in 

 the Permian deposits. 



Amono'st the molluscous animals we have members of 

 the very highest known class, namely, the Cephalopods, or 

 cuttle-fish class ; and amongst articulated animals we find 

 Irilobites and Eurypterida, which do not belong to any 

 incipient worm-like group, but are distinctly differentiated 

 Crustacea of no low form.^ 



We have in all these animal types nervous systems dif- 

 ferentiated on distinctly different patterns ; fully formed 

 organs of circulation, digestion, excretion, and generation ; 

 complexly constructed eyes and other sense organs. In 

 fact we have all the most elaborate and complete animal 

 structures built up, and not only once ; for in the fishes 

 and mollusca we have (as described in the third chapter 

 of this work) the coincidence of the independently de- 

 veloped organs of sense attaining a nearly similar com- 

 plexity in two quite distinct forms. If, then, so small an 

 advance in organization has been made in fishes, molluscs, 



1 Dr. Scudder " has lately found a fossil insect in the Devonian for- 

 mation of New Brunswick, which is furnished with the well-known 

 tympanum or stridulating api)aratus of the male Locustidie." (Trans. 

 Knt. Soc, Third Series, vol. ii., quoted in Darwin's "Descent of Man," 

 vol. i. p. 360.) 



