DIFFERENCES BETWEEN DIFFERENT ORGANISMS. 29 



nutritive organs at all, at any rate of a permanent nature. 

 The prehension of food is effected entirely by the inter- 



Fig- 4- — A, Amoebze developed in organic infusions, vtry greatly magnified 

 (after Beale) ; B, Amcria princeps (after Carter). 



vention of temporary fingers or processes of the body-sub- 

 stance, which can be thrust out at will from any point of 

 the surface of the body, and which, when retracted, melt 

 into the protoplasmic body without leaving a trace behind. 

 There is no mouth, and any particle of food seized by one 

 of these temporary arms is simply engulfed in the soft 

 body, as one might thrust a stone into a lump of dough. 

 There is no digestive cavity, and there are no digestive 

 organs of any kind. Nevertheless the Amceba possesses to 

 the full the power of assimilating the materials which it 

 takes as food, of making out of these the substances which 

 it needs for its growth and nourishment, and of rejecting all 

 that may be useless. The fluid which is manufactured out 

 of the food, and which may, in a general sense, be said to 

 correspond to the blood of the higher animals, is probably 

 propelled to all parts of the body by means of a little con- 

 tractile bladder, which dilates and closes at regular intervals. 

 If this interpretation of the facts be correct, the Amceba is 

 furnished with what may be regarded as a very rudimentary 



