THE ARTIFICIAL PRODUCTION OF SPORES IN 



MONAS BY A REDUCTION OF THE 



TEMPERATURE. 



ARTHUR WHITE GREELEY (FROM THE HULL PHYSIOLOGICAL LABORATORY 



OF THE UNIVERSITY OK CHICAGO). 



The processes of reproduction among the Protozoa present 

 many interesting problems from the physiological point of view- 

 Aside from the so-called sexual reproduction, which is always 

 preceded by the conjugation of two similar or slightly differen- 

 tiated individuals, there exist many forms of asexual reproduc- 

 tion, varying from the simple division of the parent organism into 

 two, or in some cases as many as eight, daughter cells, to the 

 more complicated processes of encystment and spore formation. 

 The processes of encystment and spore formation may be pre- 

 ceded by conjugation, but in most cases they are simply a 

 direct transformation of the motile organism into a resting form. 

 Surprisingly little is known about the physical and chemical con- 

 ditions which determine the transformation of Protozoa into cysts 

 and spores. 



It has generally been observed that when a pond, in which the 

 organisms live, begins to dry out, cysts are formed. This fact 

 caused Rhumbler and Cienkowsky 1 to undertake a series of ex- 

 periments. They kept cultures of Infusoria in small, loosely 

 covered dishes, and allowed the water to gradually evaporate. 

 Before the evaporation had become complete, all the Infusoria 

 had formed cysts. Doflein 2 has repeated these experiments and 

 has confirmed the results of Rhumbler and Cienkowsky. He 

 found that after a long-continued evaporation of water the cysts 

 would further break up into many small spores, thus proving 

 that the processes of encystment and spore formation are iden- 

 tical. Other investigators attributed this encystment to a lack of 

 oxygen, rather than to the evaporation of the water. Maupas 3 



Cienkowsky, Archiv. filr Mikroscopische Anatotitie, 1866, I., p. 203. 



2 DoHein, Archiv fi'ir ProthtcnkuiiJe, 1902, I. 



3 Maupas, Archives de Zoologie Experimental, 1888, VI., p. 165. 



165 



