Reactions of Molosoma to Chemical Stimuli 53 



exhausting. Readjustment of equilibrium through movement 

 approaches a minimum. Ma}' be produced by high temperature 

 or excessive light. 



MATERIAL I OR EXPERIMENTS 



Two species of ^olosoma were used in the course of these 

 experiments. One, probably A. quaternarium, Ehrenberg, was 

 found in great abundance in old paramcecium cultures. The basis 

 of these cultures usually consisted of partially decayed leaves and 

 grass from near the shore of a small pond in the Botanical Gardens 

 of the University of Pennsylvania. The fact that the materials 

 from which these cultures arose was gathered when dry suggests 

 either that the .^olosoma come from encysted animals or from 

 eggs. I have not been able to discover whether they come from 

 one or both. The hfe history of this species seems to undergo 

 periodic changes (Vedjovsky, 1892), quite different from that of A. 

 tenebrarum. The cultures were always several weeks old before 

 the .^olosoma appeared. When first discovered they always were 

 full grown with the fission zone of budding zooids well marked in 

 numberless individuals. From these same cultures after exten- 

 sive proliferation for two or three months, the whole colony of 

 y^olosoma sometimes disappeared in the course of a single night. 

 I examined the sides of the jar and much of the debris at the bot- 

 tom but could not find anything that was suggestive of the causes 

 or results of this phenomenon. Beddard ('92) had the same 

 experience but later discovered the encysted i5^olosoma. He 

 attributes the encystment to the approach of cold weather. My 

 cultures evidently suffered from the introduction of some patho- 

 genic conditions which destroyed them. 



The other species, probably A. tenebrarum (Vedjovsky) was 

 gathered in large quantities from the slime on loose stones along 

 the shores of the Schuylkill River, just below Flat Rock Dam, a 

 few miles north of Philadelphia. 



These species, with a number of slime covered stones were pre- 

 served indefinitely in 8 inch battery jars. Other cultures of A. 

 tenebrarum were frequently secured by placing old water hya- 



