Lect. I.] LOW ANCESTRAL TYPES. 1 1 



The early transformations of those types which have 

 no larval stage I look upon as the unused equivalents 

 of the metamorphic steps of types, which, like insects, 

 have an active larval stage, or stages. These transi- 

 tory, unused stages are, manifestly, of an historical 

 import ; they suggest to the Darwinian lower and still 

 lower types of ancestral animals — the Fauna of a 

 bygone time. And this view of the matter is well 

 borne out by what we already know of the structure 

 of the Prototheria, or Monotremes, and of the Meta- 

 theria, or Marsupials. It is also borne out by every- 

 thing I have seen, as yet, in the structure and de- 

 velopment of the other groups of the Vertebrata, as 

 they rise one above the other in the order of morpho- 

 logical excellence. 



The perfection of every organ for its special use in the 

 adult nlakes it the more noteworthy that there are so 

 many things to be found, during growth, that are not 

 only useless, but, as a rule, transient — some of them, 

 however, are permanent. The doctrine of Final Pur- 

 pose, on its old platform, and taken as if it were the 

 conclusion of the matter, whoUy fails to explain these 

 rudiments, or remnants — these useless odds and ends of 

 forgotten organs. Whether transitory, or permanent, 

 they are the opprobrium of the teleologist who has not 

 studied the growth of the embryo, but they are goads 

 and spurs to him who devotes himself to the study of 

 Development. Yet the doctrine of Final Causes is not 



