CONVERGENCE. 



151 



every manual of comparative anatomy affords testimony 

 that the series of vertebrate animals now living, present 

 series of development which negative the sudden and 

 incomprehensible origination of these organs in an im- 

 mediate state of completion. How they appeared in yet 

 lower grades than are exhibited in the true fishes of the 

 present time we may learn in part from the lancelet, and in 

 part we may picture to ourselves from the corresponding 

 sensory apparatus of the lower Mollusca, Articulata, and 

 Annulosa. With reference to the objections to his doc- 

 trine arising from the arrangements of the most perfect 

 organs, Darwin has said that he would abandon his 

 whole theory if it can be shown that any of these or- 

 gans could not possibly have been formed from 

 lower grades, by improvement slowly acquired. This 

 demonstration no one has yet undertaken, nor will 

 it ever be undertaken with success, as every deeper 

 penetration into the comparative anatomy of the sensory 

 apparatus affords evidence to the contrary. In order 

 to understand the presumptively faultless sensory organs 

 and their derivation from a lower grade, it is of supreme 

 importance to bear in mind the circumstance first ex- 

 hibited by Helmholtz in the eye, that besides a num- 

 ber of perfections, they likewise possess a number of 

 imperfections, and purposeless or obstructive arrange- 

 ments. 



But we must examine another point, which may 

 awaken doubts as to the admissibility of the doctrine 

 of Descent, though, strangely enough, it has as yet been 

 turned to little account by adversaries, and only inci- 

 dentally touched upon by Darwin. In the " Origin of 

 Species," he states, that H. C. Watson, we know not 



