EFFECTS ON THE PROTOZOA 21 



daughter nuclei (as in conjugation), a process interpreted as "self-fertilization." 

 Kasanzeff distinguishes two phases of inanition, the second phase beginning 

 with the disintegration of the macronucleus. 



Wallengren ('02), a pupil of Verworn, studied "hunger cultures" of Parame- 

 cium caudatum (also of Colpidium colopoda). He also divided the inanition 

 period of about 15 days into two phases. In the first phase of 8 or 9 days, the 

 reserve food material becomes exhausted. Through the disappearance of the 

 food-granules and food-vacuoles, the endoplasm becomes transparent and is 

 greatly reduced in volume. In the second phase, the endoplasm is attacked 

 and numerous vacuoles of variable size arise, "die wahrscheinlich durch osmot- 

 isch wirkende Zellprodukte entstanden sind" (see Fig. 6). The contractile 

 vacuoles are reduced, and the ectoplasmic organs (trichocysts, cilia) become 

 smaller and sometimes partially consumed. In the macronucleus appear 

 granules which fuse to form a mulberry-like mass (nucleolus), which persists 

 while the remainder of the macronucleus becomes progressively vacuolated, 

 deformed, and often finally fragmented and largely resorbed. Of all the cell- 

 organs, the micronucleus alone resists the destructive effects of inanition, 

 although it may show changes preliminary to a normal division. Normal 

 conjugation may occur during the early stages of inanition. "So schreiten 

 also bei der einzelnen Zelle die Inanitionserscheinungen von den unwichtigeren 

 Teilen zu der wichtigeren fort, die unentbehrlichsten halten am langsten stand." 



In size, Wallengren's paramecia were reduced in ten days from 0.25-0.3 mm. 

 to 0.16-0.17 mm. in length, and from 0.07-0.08 mm. to 0.028-0.042 mm. in 

 breadth. (The loss in Colpidium was relatively even greater.) In the later 

 stages, the breadth may be increased by enormous vacuolation. Death may 

 occur either suddenly, by rupture of the cell-membrane; or more slowly, with 

 gradual decrease of the cell until death from exhaustion. On refeeding, the 

 paramecia may gradually regain their normal size and structure, even when 

 markedly vacuolated by fifteen days of inanition. 



Most of the observations of Wallengren upon Paramecium caudatum were 

 verified by Calkins ('02, '04), who found that inanition is unfavorable to con- 

 jugation. He also studied the somewhat similar periodic " depression " phenom- 

 ena, and found them to occur independent of nutrition. 



Another extensive investigation was made by Chajinski (Chainsky) ('03, 

 '06), who made over 15,000 observations on starving Paramecium caudatum. 

 His results in general are very similar to those of Kasanzeff and Wallengren. 

 In the earlier period, he found disappearance of the food-vacuoles, with succes- 

 sive vacuolation of the endoplasm, and vacuolation (sometimes division) of the 

 macronucleus. In the later stages, the ectoplasm also becomes vacuolated, the 

 macronucleus greatly vacuolated and fragmented, and the entire cell markedly 

 deformed. The micronucleus persists unchanged. Conjugations may occur 

 in the earlier stage of inanition. 



Jennings ('08) made a careful and extensive statistical study of size, includ- 

 ing the effects of varied nutrition, in Paramecium caudatum and Paramecium 

 aurelia. "Pure line" cultures were utilized. A large number of P. caudatum 

 were taken from a 24 hour hay-infusion culture, and were kept in a small 



