EFFECTS ON THE PROTOZOA 1 7 



by Geddes and Thompson ('01). The studies of Maupas ('88, '89) and of 

 numerous more recent investigators, however, have shown that the life cycle of 

 the protozoa, with its phases of sexual and asexual reproduction, is apparently a 

 very complicated process, involving both internal and external factors. Among 

 the latter, inanition is doubtless an important factor, which under certain condi- 

 tions may induce conjugation. This was observed by Maupas and others in 

 numerous species of Infusoria. Hertwig discovered that when low temperature 

 cultures (which have a relatively large nucleus) are placed at a high temperature 

 and kept without food, an artificial "depression" is produced, which leads to 

 conjugation. This was confirmed by Prandtl ('06) for Didinium, and by Popoff 

 ('07) for Epistylis. Conjugation has been observed in the earlier stages of 

 ordinary inanition in Paramecium by Kasanzeff ('01), Wallengren ('02) and 

 Chainsky ('06); but Calkins ('02) andLipska ('10) found inanition very unfavor- 

 able to conjugation. It is evident that further research is necessary in order to 

 clear up this fundamental problem. 



Recovery upon Refeeding. — The protozoa show an astonishing capacity for 

 recuperation upon careful refeeding after inanition. Maupas ('88) found that 

 an atrophic Stentor regained its original size in two days of abundant realimenta- 

 tion, which evidently involved an increase of over 100 times its reduced volume. 

 Joukowsky ('98) observed a similar remarkable capacity for recuperation in 

 Pleurotrichia. In Paramecium, Wallengren ('02) found a normal recovery 

 possible, even in the greatly vacuolated condition after fifteen days of inanition. 

 Lipska ('10), however, found recovery in general possible only up to four or five 

 days of inanition. The process of recovery is the inverse of that during inani- 

 tion, and cell-divisions begin after three to five days of refeeding. Nirenstein 

 ('10) observed regeneration of endoplasmic fatty granules in Paramecium 

 within a few hours of refeeding. Jennings ('08) noted that variability in size is 

 increased during refeeding, some individuals recuperating more rapidly than 

 others; but the normal condition is eventually restored. 



Effects on the Various Species of Protozoa 



Protozoa Other Than Infusoria. — Among the unicellular animals constitut- 

 ing the phylum Protozoa, only a few observations as to the effects of inanition 

 have been made upon forms outside of the class Infusoria. Brass ('83) noted 

 that in starving Amebae and Gregarinae, as well as in Infusoria, the chromatic 

 nuclear substance becomes resorbed, serving (according to his interpretation) 

 as a reserve nutritive material. Schaudinn ('99) observed that in Trichosphaer- 

 ium Sieboldii (a species of Foraminifera) during starvation the first change is a 

 retraction of the pseudopodia in two or three days, and a resorption of the nutri- 

 tive granules. "Zugleich mit diesen Vorgangen beginnen die Zellkerne sich an 

 einzelnen Stellen zu kleinen Gruppen zusammenzulagern. Nachdem das 

 Plasma rein geworden ist, wird dasselbe grob vakuolisiert, und zwar scheint 

 diese Vakuolisierung von der Peripherie gegen das Zentrum vorzuschreiten. 

 Im weiteren Verlaufe vereinigen sich die einzelnen Kerngruppen zu einer einzigen 

 grossen Gruppe, und die Zelle rundet sich kugelig ab. Die Vakuolisierung 



