124 



GENERAL BIOLOGY 



The food is taken in at any part of the body. This food consists of tiny 

 aquatic plants, other single-celled animals, bacteria, and various animal 

 and vegetable matter. 



It is of special interest to note that when food is taken by Amoeba 

 the animal really places its body around the food (Fig. 46). Experi- 

 ments with inorganic substances, such as a drop of chloroform in a 

 watch glass of water have shown that the chloroform will take in sub- 

 stances like shellac and parraffine and reject wood, glass, etc. It must 

 not be forgotten, however, that these substances which are thus accepted 

 by the inorganic drop of liquid are those which normally adhere to 

 chloroform. But with Amoebae the majority of food substances 

 do not adhere to the surface of the animal, and so again there is con- 

 siderable dissimilarity between the experiment and the actual facts in 

 the case. 



In digestion the food vacuoles have been embedded in the endo- 



plasm. The cell wall pours out 

 a secretion of some mineral 

 acid supposedly HC1. This di- 

 gestive fluid seems to dissolve 

 only proteid substances and has 

 no effects upon fats and carbo- 

 hydrates. Hofer performed an 

 interesting experiment by cut- 

 ting an Amoeba in two parts 

 after it had just been well fed 

 and the part that did not have 

 the nucleus was unable to di- 



A, Amoeba encysted. 



B, Amoeba ingesting a plant, p, retracted pseudo- gCSt lOOd. 



podium; dt, plant (diatom) taken in as food, cv, A u -i j- 



contractile vacuole ; f.v., food vacuole ; n, nucleus. A SOmewnat Similar COndl- 



tion will be found a little later 



in the study of the earthworm, in which case, if the animal be cut in 

 two behind certain segments the forepart of the animal, which contains 

 the important organs, will regenerate a new tail. Whereas, the tail-part 

 which has been cut off will regenerate another tail. This latter animal 

 having no organs, must necessarily starve to death as it has no way of 

 ingesting food. 



After digestion has taken place in Amoeba, any indigestible particle 

 may be thrown out at almost any point on the surface of the animal. 

 These indigestible substances are probably heavier than the protoplasm 

 itself, so this heavy portion sinks through the lower part of the animal 

 body. Then as the animal moves away it leaves the indigestible solid 

 particle behind. 



There is no circulatory system proper in a one-celled animal, so that 

 after the food has been digested it must be absorbed and passed into 

 the body substance proper of the animal. Here we come to a new term, 



Fig. 46. 



