AMCEBJE. 93 



nutrient material, and then closing in around them, press them 

 into the midst of the granular central mass. Here they sojourn 

 some little time, and during this period, no doubt, any nutritive 

 properties they possess are extracted from them, and they are 

 then ejected from the plastic substance. This form of assimilation 

 demands no previous preparation of the food, such as we shall see 

 takes place in the alimentary tract of man and in the special or- 

 gans of the higher animals ; yet it is a form of digestion adequate 

 at least to the requirements of this simple organism. The re- 

 peated alteration of the different parts of the protoplasm in rela- 

 tion to one another and the surrounding medium during the flow- 

 ing hither and thither of the currents, produces not only a change 

 in the shape and position of the animal, but also acts as a means 



Two different forms of Amrebse in different phases of movement. Those on the left 

 after Cadiat. A and B show an outer clear zone (Gegenbaur ) 



of distributing the nutriment to the different parts of the body, 

 and of collecting and carrying to the surface the various pro- 

 ducts of tissue decomposition ; thus the streaming protoplasm 

 does the work of a circulating fluid such as we see in the more 

 elaborate organisms for the distribution of nutriment and elimi- 

 nation of waste materials. The surface of the amoeba is suffi- 

 cient to allow of the gas interchange necessary for life, and by 

 means of the ever-changing material exposed, sufficient oxygen 

 is taken for its tissue combustions, and so a function of respira- 

 tion is established. The growth that results from the perfect 

 performance of these vegetative functions proceeds until the 

 maximum size is attained, and further nutritive activity is then 



