134 COMPARATIVE ANATOMY 



direction of that point, and a pseudopod-like process may be 

 emitted. The streaming movements in the droplet, however, 

 are different from those observed in an Amoeba, and in this 

 as in all other attempts to identify vital with simple physico- 

 chemical processes, the comparison breaks down under the 

 test of rigorous criticism. The droplet of oil and salt does 

 not ingest food, does not assimilate, does not grow and 

 reproduce its kind. The most essential vital phenomena 

 are wanting and it cannot be said, in any sense, to live. 

 Moreover, if watched for a long time, the movements of an 

 Amoeba are seen to be of a purposive character that is to 

 say, they are clearly adapted to the necessities of the 

 organism, as is evident when an obstacle is met with, or when 

 the animalcule endeavours to seize and ingest some object 

 that rolls away from it, or attempts to capture a smaller 

 member of its own kind for food. * 



Like all indisputable animals an Amoeba takes into its 

 interior or, as we say, ingests solid food, consisting of vege- 

 table or animal matter, Oscillaria, Diatoms, and even other 

 Protozoa. These substances may generally be seen in the 

 central part of the cytoplasm, and careful examination shows 

 that each separate morsel of food is enclosed in a space filled 

 with fluid, called a food-vacuole. The vacuole however is 

 formed subsequent to the ingestion of the food, and is not 

 merely a droplet of water taken in along with it, but a 

 secretum of the protoplasm. There is no special orifice nor 

 even a soft spot in the protoplasm where solid food is taken 

 in. The pseudopodia come into contact with some food- 

 substance ; they embrace it, flow round it, meet above and 

 below it, and finally enclose it. Blochmann has described 

 how Amxba proteus catches the agile infusorian Cydidium 

 glaucoma in this simple manner. The Cyclidium seems to be 

 fatally attracted to the Amoeba, swims towards it, and lies 

 between its pseudopods. In this position it is enclosed above 

 and at the sides by the flowing movement of the protoplasm ; 

 it seeks awhile to escape from the death-chamber, but it is 

 finally enclosed ; and, when enclosed, a vacuole is secreted 



* For a further account of the movements, habits and reactions of 

 Amoeba, the reader should consult the very interesting work of H. S. 

 Jennings, "Contributions to the Study of the Behaviour of the Lower 

 Organisms." Published by the Carnegie Institution of Washington, 1904. 



