TELEOLOGY AND PHYSIOLOGY. 47 



how all these facts comprised under Morphology, Ph}'^!- 

 ology, and Chorology have come to be what they are ; 

 and the attempt to solve this problem leads us to the 

 crown of Biological effort, ^Etiology. When it supplies 

 answers to all the questions which fall under these four 

 heads, the Zoology of Crayfish will have said its last 

 word. 



As it matters little in what order we take the first three 

 questions, in expanding Natural History into Zoology, 

 we may as well follow that which accords with the history 

 of science. After men acquired a rough and general 

 knowledge of the animals about them, the next thing which 

 engaged their interest was the discovery in these animals 

 of arrangements by which results, of a kind similar to 

 those which their own ingenuity effects through mechanical 

 contrivances, are brought about. They observed that 

 animals perform various actions ; and, when they looked 

 into the disposition and the powers of the parts b}^ which 

 these actions are performed, they found that these parts 

 presented the characters of an apparatus, or piece of 

 mechanism, the action of which could be deduced from 

 the properties and connections of its constituents, just 

 as the striking of a clock can be deduced from the 

 properties and connections of its weights and wheels. 



Under one aspect, the result of the search after the 

 rationale of animal structure thus set afoot is Teleology ; 

 or the doctrine of adaptation to purpose. Under another 



