LAMARCK. 169 



His conception of the initial causal relation of 

 the desires and wants of animals is illustrated in 

 the following paragraphs: 



" I conceive that a Gasteropod mollusc, which, as it crawls 

 along, finds the need of touching the bodies in front of it, makes 

 efforts to touch those bodies with some of the foremost parts of 

 the head, and sends to these every time quantities of nervous 

 fluids as well as of other liquids ; I conceive and say, that it must 

 result from this reiterated afflux towards the point in question, 

 that the nerves which abut at these points will, by slow degrees, 

 be extended. Now, as in the same circumstances, other fluids of 

 the same animal flow also to the same places, and especially nour- 

 ishing fluids, it must follow that two or more tentacles will appear 

 and develop insensibly on the points referred to." 



As illustrating the sensitiveness of lowly organized 

 animals to the action of evironment, he cites a series 

 of his observations upon Hydra, when moving about 

 in search of light. 



Numerous other examples are given of the sup- 

 posed origin of other parts of the body, among which 

 we may select his account of the origin of the hoofs 

 in mammals : 



"All mammals sprang from saurians, more or less similar to 

 our crocodiles. They first appeared under the form of amphib- 

 ian mammals with four feebly developed limbs. These primi- 

 tive forms divided in the manner according to which they fed. 

 Some, accustoming themselves to browse upon shrubs, became the 

 source of the ungulates. Advancing upon the earth, they experi- 

 enced the need of having longer limbs, their toes became elongated, 

 and the habit of resting upon their four feet during the greater 

 part of the day has caused a thick horn to arise, which envelops 



