INTERACTIONS OF PROTOPLASMIC MASSES. l.>7 



ions, and thus answer some of the hitherto perplexing questions. 

 In the first place, they show that both physiological and morpho- 

 logical variations do appear among protozoa reproducing \ege- 

 t, nively, and that such variations can be hastened by alurin- 

 ihr environments; and secondly, that these changes are not due 

 to inherited variations which persist for very long periods of time. 

 for they could be reversed within a few days. Unquestionably. 

 certain heritable variations often arise in cultures, and seem to 

 persist for some time afterwards; but, in our experiments at 

 least, if the organisms in which these changes are manifested are 

 left in the same surroundings, undisturbed, they tend to revert 

 to the normal type, while if placed in a different environment 

 where selection would be affective, or if artificial selection is 

 practiced, the aberrant characteristics may be continued, or even 

 emphasized. 



In a similar manner the physiological status of organisms is 

 subject to modifications. Adjustments are constantly being 

 made as a result of the ever changing surroundings. The ques- 

 tion seems to resolve itself into one of environmental factors, of 

 which food is by no means the least important. The only diffi- 

 cult factor to control in these experiments was the bacU-ri.il 

 growth in the culture media. In fact, the rapid differentiation 

 observed when unlike culture media were used, was probably due 

 to a change in the character of the bacterial flora produced by the 

 action of the environment; for if the action had been direct, in 

 some cases at least, physiological differences should have occurred 

 \\ iihin a few hours after the organisms were exposed to it. 



SUMMARY AND CONCLUSIONS. 



i. Like Dijjlugia, Arcclla polypora will, under favorable con- 

 ditions, reappropriate its detached fragments of protopla-m by 

 lu-ion. 



j. .1. polypora is not attracted by a pseudopodial fragment of 



'Jiigiu. If accidental contact is made the fra^im-m 

 as a mechanical obstruction. 



,v Fusion will take place between one individual and a proto- 

 plasmic fragment of a closely related -]>t > -mien. 



4. Two distantly related individuals, which ha\e not been 

 kept in the same receptacle, will be attracted by each other'- 



