ADAPTATIONS 147 



quotation has been taken is that the actions 

 of living things are the result of taetisms and 

 that these are due to changes in the chemical 

 composition or reactions of the colloids of 

 which the body is made up. Of what nature, 

 one may fairly ask, are those chemical com- 

 pounds which never react twice in the same 

 way? 



Even amongst the smallest and simplest 

 forms of animal life it is possible to come across 

 actions which are undoubtedly purposive. Purposive 

 One or two examples of these may now actlons 

 be cited. 



Cienkowski * has described a little naked 

 unicellular organism, very much like the 

 Amoeba which formed the subject of our study 

 in an earlier chapter. Like the Amoeba it lives 

 in water and like it too it moves by a kind of 

 crawling motion due to the protrusion of pro- 

 cesses from its own body up to which the 

 remainder of the body is drawn. Living in 

 the water it is, of course, surrounded by a 

 great variety of water-plants small and large, 

 any of which, one might have supposed, would 

 have sufficed for its food. Such, however, is 

 not the case. Of all the algae or water- 

 vegetables by which it is surrounded, it in- 



* The instances now about to be narrated have been de- 

 tailed by Pauly in his book, Darwinism** und Lamarckis- 

 mus, Miinchen, 1905, s. 147. 



