ON THE FEEDING HABITS OF AMEBA 535 



If these amebas are disturbed, as when transferring them from 

 the culture vessel to the slide or the watch glass for observation, 

 they sometimes assume a clavate or a spatulate form ; but when 

 undisturbed in their culture they are generally of a shape that 

 might best be described as stellate. 



These amebas thrive best in cultures where diatoms, desmids, 

 and oscillaria are growing. On account of their peculiar feeding 

 habits, these amebas are referred to in the following pages as 

 raptorial amebas, to distinguish them from the granular type. 



The raptorial amebas are easily reared in cultures if slowly 

 decaying leaves only are placed in the culture vessels ; but other- 

 wise the cultures may be made up as for the granular type. The 

 chances of success are improved if some diatoms and oscillaria 

 are added. 



I have found little difficulty in obtaining amebas from ponds 

 around Knoxville, during every month of the year. Shallow 

 ponds not subject to floods, in which cat-tails grow, may be con- 

 sidered as almost sure to yield amebas if cultures are made as 

 outlined above ; or they may be obtained directly if the decanted 

 water is poured into a deep vessel and allowed to settle over 

 night, and the sediment then drawn off with a pipette and placed 

 into a petri dish for examination under the binocular microscope. 



The raptorial and the granular types are seldom found together, 

 in numbers. Raptorial amebas have been seldom met with in 

 granular cultures, but a few straggling, sick looking, granular 

 amebas have nearly always been found in the cultures of the 

 raptorial type. 



WTiether these two types represent two or more species, or 

 only different stages in the life cycle of a single species has not 

 yet been determined. A considerable number of the experi- 

 ments had been performed before the difference in the behavior 

 between these two types became convincing. But this point is 

 now under investigation and I hope soon to publish a paper which 

 shall clear up this matter. 



It is almost needless to say that it is of fundamental impor- 

 tance in physiological studies to know just what animals were 

 used for observation and experiment. It is easy to see that the 



