ADAPTATIONS 91 



of animal life it is possible to come across actions Purposive 

 which are undoubtedly purposive. One or two* 

 examples of these may now be cited. 



Cienkowski * has described a little naked uni- 

 cellular 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 processes from its own 

 body up to which the remainder of the body is 

 drawn. Living in the water it is, of course, sur- 

 rounded 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 invariably seeks out 

 one and one only, namely spirogyra and makes its 

 meal off that. 



Obviously it finds that the spirogyra suits it 

 best or, as we should put it, it prefers spirogyra 

 to any other kind of food, just as we too have our 

 preferences in the same matter. 



The same observer in relating the habits of 

 another unicellular organism, called colpodella Coipodeiu 

 pugnax, tells us that it lives solely on an alga 



1 The instances now about to be narrated have been detailed 

 by Pauly in his book, Darwinismus und LamarcJcismus, Miinohen, 

 1905, s. 147. 



