CHAR A CTERISTICS. 



55 1 



generally found on the ooze of ponds, or the under surface of the leaves of aquatic 

 plants, but especially amongst conferva, in clear gently flowing water. When first 

 caught, the animal will appear as a tiny yellowish semitranslucent globular speck, 

 about one-hundredth of an inch in diameter ; presently it becomes beaded with 

 rounded projections, some of which grow longer at the expense of others and of 

 the body, and may give off one or two branches. By the projection of these 

 processes, or pseudopods, the amoeba moves along in the direction of the longer 

 ones. " Sometimes," writes Leidy, " the animal creeps onward in a flowing manner 

 with comparatively simple cylindroid form, occasionally emitting a single pseudopod 

 on one side or the other. More commonly, in movement, it assumes a dendroid or 

 palmate form, or sometimes, diverging from the directly onward course, it becomes 

 more radiate in appearance. Not unfrequently it assumes more or less grotesque 



peoteus animalcule, (highly magnified). 



shapes, in which almost every conceivable likeness may be imagined." The body, 

 of the amoeba is full of granules, which render it semiopaque, with the exception 

 of a thin clear outer hyaline zone, and near the centre is a globular or discoid body, 

 known as the nucleus, composed of a denser protoplasm than that which surrounds 

 it. Division of an amoeba into two is preceded by division of the nucleus. Near 

 the latter is a clear spherical space — the contractile vacuole — which gradually 

 expands, rather suddenly collapses, and reappears at the same spot, the systole and 

 diastole being slow and continuous. The contractile vacuole contains a clear liquid, 

 which is expelled on the collapse of the vacuole. This organ probably serves the 

 double function of respiration and excretion. The amoeba is omnivorous, but is 

 chiefly vegetarian, and browses on tender leaves, or feeds on diatoms and other 

 algse ; it surrounds the food-particle or organism with the protoplasm of its body 

 or of a pseudopod, and the ingested particle sinks in, surrounded by a zone of 

 water; frequently there are several food-balls in the body of the animal. The 



