DEGENERATION. 55 



I believe that I shall have the assent of every 

 naturalist when I say that the vertebrate character of 

 the Ascidians and the history of their degeneration 

 would never have been suspected, or even dreamed of, 

 had the Ascidian tadpoles ceased to appear in the 

 course of the Ascidian development at a geological 

 period anterior to the present epoch. 



This being the case, it must be admitted that it is 

 quite possible — I do not say more than possible 

 • — that other groups of animals besides parasites, 

 Barnacles, and Ascidians, are degenerate. It is 

 quite possible that animals with considerable com- 

 plexity of structure, at least as complex as the 

 Ascidians, may have been produced by degeneration 

 from still more highly-organized ancestors. Any 

 group of animals to which we can turn may possibly 

 be the result of degeneration, and yet offer no evidence 

 of that degeneration in its growth from the Qgg. 



Accordingly, wherever we can note that a group 

 of organisms is characterized by habits likely to lead 

 to degeneration, such as I have enumerated, viz., 

 parasitism or immobility, or certain special modes of 

 nutrition, or again, by minute size of its represen- 

 tatives — there we are justified in applying the 



