THE ARTIFICIAL PRODUCTION OF SPORES. l6/ 



was the rapid or extensive changes of temperature. As long as 

 the bulk of water in a pond is large, the daily changes of the 

 temperature of the air will only cause a slow or slight variation 

 in the temperature of the pond. But where the bulk of water is 

 small, the temperature of the latter will follow rapid changes in 

 the temperature of the air more rapidly and completely. In 

 order to test this idea, he suggested that I try whether or not, 

 through sudden changes of temperature, organisms might be 

 caused at any time to reproduce asexually instead of sexually. 

 The experiments were first performed on Stcntor with the results 

 already described in a previous paper. 1 It was found in these 

 experiments that by lowering the temperature the animal would 

 go into a resting stage, which in appearance resembled a cyst ; 

 but in no case did I obtain spores. These results could not be 

 obtained by raising the temperature. 



During the past year the low temperature experiments have 

 been continued on several other Protozoa, and in all of them 

 structural changes similar to those already described for Stcntor 

 have been obtained. But in one form, Monas, our original pur- 

 pose has been carried out, namely, the artificial production of 

 spores by means of variations in the temperature. 



Monas is a small flagellated Infusorian, of an exceedingly sim- 

 ple structure, and occasionally appears in great numbers in 

 cultures that have been prepared for Paramcrcia. It can be easily 

 maintained in the laboratory in great quantities by adding to the 

 culture from time to time a little bread, upon which the Monads 



FIG. I. The adult Monas. 



thrive surprisingly. In all the experiments the Monads were 

 isolated in small covered dishes, and the supply of water kept 

 constant by frequent renewal from the aquaria in which the 

 animals had been reared. The temperature was lowered to the 

 desired point by placing the dishes in a refrigerator in which con- 



1 Greeley, American Journal of Physiology, 1901, VI., p. 122. 



