REACTIONS OF CELL-BODIES OF DIFFLUGIA. 23 



are separated and distributed in water, will reassemble and form 

 new individuals. 



The conditions of life under which the above animals live im- 

 pose a risk of the body parts. Difflugia is protected, to a certain 

 extent, from external environments by its shell, and perhaps also 

 by the formation of a plug of mucus about the mouth of its shell 

 when unduly stimulated. Nevertheless, in sending out long, slen- 

 der pseudopods, it, too, runs a risk of losing some of its proto- 

 plasm, for, as recorded by Verworn (1890), when the projecting 

 pseudopods are strongly stimulated, they are frequently jerked 

 back so suddenly as to whip off their ends. 



The Organisms. 



Various species of Difflugia were used in these experiments, all 

 of which gave similar results. However, it was found that D. 

 acuminata, D. corona, D. pyriformis, D. spiralis, and D. vulgaris 

 were* more favorable for study because of the nature of their 

 pseudopodial formation, and also because they commonly drag 

 themselves after their advancing pseudopods with the shell in a 

 reclining position, so that the mouth of the shell and the bases of 

 the pseudopods can be seen easily. This feature also affords a 

 better opportunity for cutting off pseudopods without danger of 

 striking the shell. 



Methods. 



(a) Collecting. 

 The animals were collected in small puddles in a cow pasture 

 near the University of Virginia. These puddles were near a fresh 

 stream and frequently obtain a supply of fresh water, due to rains, 

 and the overflowing of the banks of the stream. In the same 

 puddles other protozoa, fresh-water Crustacea, and various algae 

 are also found. The brown ooze and vegetable matter on the 

 bottom of these little pools were carried to the laboratory in fruit 

 jars, then allowed to stand for several hours, after which the sur- 

 face of the sediment, along with sufficient water to fill the vessel 

 to a depth of approximately five millimeters, was transferred to 

 Petri dishes. The organisms can be kept in this way for several 

 weeks, provided fresh water is added occasionally. In these ex- 

 periments no attempt was made to maintain pure line cultures. 



