534 ASA A. SCHAEFFER 



taken carefully from the bottom of a shallow pond where cat- 

 tails grow, were brought into the laboratory and then thoroughly 

 shaken up with three or four liters of pond water. The water 

 was then decanted and poured into flat-bottomed glass dishes, 

 about twenty centimeters in diameter, to a depth of two or three 

 centimeters. Enough of the dead leaves w^ere placed in each 

 dish so that if they were uniformly spread out and gently pressed 

 down they would form a layer one or two millimeters thick. The 

 cultures were exposed to full north light, but not to direct sun- 

 light. The dishes were covered with glass plates, leaving a 

 small opening for ventilation. Of every dozen cultures set up 

 in this way, at least two or three proved successful. 



During the winter and early spring when my own cultures 

 sometimes ran out, and for comparison with my own at other 

 times of the year, granular amebas were obtained from Powers 

 and Powers, Lincoln, Nebraska. 



Raptoj^ial amehas. This type of ameba contains only a very 

 few granules which are much larger than those in the granular 

 amebas, and are very irregular in shape. These amebas appear 

 much clearer than those of the granular type. The pseudopods 

 are numerous when moving on a fiat surface. They are dorso- 

 ventrally flattened. Frequently there is no 'main' pseudopod, 

 and the direction of movement is, therefore, somewhat uncer- 

 tain. Pseudopods seem to be formed with ease, and the whole 

 ameba seems to be of a thinner consistency than those of the 

 granular type. Dead and immobile organisms are eaten very 

 seldom. Carmine, globulin, etc., are only rarely eaten. Slowly 

 moving organisms of all sizes, from small flagellates to paramecia 

 and rotifiers, and especially diatoms and desmids are the frequent 

 prey of these animals. If these food organisms do not move, 

 frequently no attempt is made to eat them; but if such organisms 

 are mechanically agitated the feeding reaction at once sets in. 

 These amebas are very responsive to mild mechanical stimula- 

 tion with a glass needle. With careful manipulation they can 

 be led about in any desired direction. They will ingest any 

 small non-poisonous object if it is properly agitated. 



