562 LORANDE LOSS WOODRUFF 



water equal to that of the entire organism in forty-six minutes, 

 and similarly Cryptochilum nigricans does the same in two min- 

 utes. In 1907 Kanitz^^ found that, within certain limits, a rise 

 of 10° of temperature caused a doubling of the rate of con'f^rac- 

 tion, while the results of Khainsky,^^ 1910, showed that in Par- 

 amaecium caudatum the vacuole contracted 2.86 times per min- 

 ute at 16° C, 6 times per minute at 23° to 25° C, and 10 times per 

 minute at 33° to 34° C, under the conditions of the experiments. 



It is clear then that excretion products in the case of many 

 organisms have a profound effect on cell division and growth, and 

 it is also clear that under favorable conditions of food and tem- 

 perature the Infusoria excrete considerable amounts of carbon 

 dioxide, together with various other end-products of metabolism, 

 which may reasonably be expected to be evident through bio- 

 logical as well as chemical tests. 



The ordinary 'hay infusion' teeming with animal and plant 

 life is a microcosm in which every organism may and probably 

 does in some degree affect the well-being of every other organ- 

 ism present. Besides the obvious influence exerted by animals 

 in feeding on other forms and by green plants through photo- 

 synthetic processes, one would expect the effects of organisms on 

 their environment by the elimination of products of their metab- 

 olism, or excretion products, to be one of the most important. 

 The interdependence of the organisms of a hay infusion is so com- 

 plex that, taken as a whole, it is almost beyond the possibility 

 of analysis, and accordingly the logical method of approach 

 to the subject is to study the interaction of isolated organisms and 

 small groups of organisms on themselves and on each other. 

 The present paper presents the results which have been obtained 

 from the study of the effects on the rate of reproduction of Para- 

 maecium of: 



1. Different volumes of culture medium; 



2. Changing the culture medium at twenty-four hour and at 

 forty-eight hour intervals; 



3. Culture medium in which rich growths of paramaecia have 

 occurred. 



" Kanitz, Biol. Zentralblatt, Bd. 27, 1907. 



" Khainsky, Archiv. f. Protistenkiinde, Bd. 22, I, p. 1, 1910. 



