THE ARTIFICIAL PRODUCTION OF SPORES IN MONAS 

 BY A REDUCTION OF THE TEMPERATURE 



Arthur White Greeley 



The processes of reproduction among the Protozoa present many interesting 

 problems from the physiological point of view. Aside from the so-called sexual repro- 

 duction, which is always preceded by the conjugation of two similar or slightly differ- 

 entiated individuals, there exist many forms of asexual reproduction, 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 preceded 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 conditions 

 which determine the transformation of Protozoa into cysts and spores. ■* 



It has generally been observed that when a pond in which the organisms live n^ 

 begins to dry out, cysts are formed. This fact caused Cienkowsky ^ to undertake a . 

 series of experiments. He kept cultures of Infusoria in small, loosely covered dishes, 

 and allowed the water gradually to evaporate. Before the evaporation had -become com- 

 plete, all the Infusoria had formed cysts. Other investigators attributed this encyst- 

 ment to a lack of oxygen, rather than to the evaporation of the water. Maupas ^ has 

 kept cultures of various Infusoria for long periods of time, and has found that some 

 of the carnivorous forms, notably Oxytrichia, form cysts after they have been deprived 

 of food. Hertwig' has observed that the same fact holds good for Actinosphserium. 

 In the same series of experiments he found, however, that the consumption of an 

 excess of food may cause encystment as well as starvation. Other cases are on record 

 also in which various carnivorous Infusoria have been seen to encyst after engulfing a 

 large amount of food. Klebs,* in a large number of experiments on fresh-water Algse, 

 has observed that in Vaucheria zoospores are formed when the filaments are transferred 

 from the light to the dark. Klebs reared Vaucheria in the following solution, used at 

 concentrations of from 0.1 to 0.4 per cent.: Ca(N03)2, four parts; MgS04, one part; 

 KNO3, one part; K2HPO4, one part; and found that when the filaments were trans- 

 ferred from this solution to distilled water, irrespective of light or dark, zoospores 

 were formed. He also succeeded in producing parthenogenetic spores in Spirogyra 

 by plasmolyzing the cells with a sugar solution. Klebs makes the general statement 

 that the formation of zoospores in Vaucheria is aided by lowering the temperature, 



1 Cienkowsky, Archiv fUr mikroscopische Anatomie, 3 Hertwig, Sitzungsberichte der Gesellschaft fUr Mor- 

 Vol, I (1866), p. 203. phologie und Physiologie in MUnchen, 1899, 



2 Maupas, Archives de zoologie expirimentale. Vol. VI * Klebs, Die Bedingungen der Fortpflanzung bei eini- 

 (1888), p. 163. gen Algen undPilzen, Jena, 1896, 



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