CHAPTER II 



EFFECTS ON THE PROTOZOA 



The effects of inanition on the protozoa are of especial importance, since 

 the changes can be directly observed under the microscope in these unicellular 

 forms. These changes are of extreme importance in interpreting the effects of 

 inanition in the higher organisms, including man. In the present chapter, 

 some of the more important results of inanition among the protozoa will first be 

 indicated briefly in relation to duration of starvation, changes in cell size and 

 form, endoplasm and ectoplasm, nucleus, reproduction, and recovery upon 

 refeeding. The changes will then be explained more in detail in the various 

 species of protozoa. 



Summary of the Effects on the Protozoa 



Period of Survival. — The period of survival during inanition among protozoa 

 in general is usually quite limited, being only a few (four or five) days in Stentor 

 and Rhizopoda without symbiotic algae. Amoeba terricola may survive ten 

 to twenty days; Amoeba proteus and Trichosphaerium, two or three weeks. 

 Paramecia may survive from three to twenty-one days. The minimum repre- 

 sents Lipska's observation for the (exhausted?) individuals immediately after 

 conjugation. Her research indicates that five to seven days more nearly repre- 

 sents the average for complete inanition. The prolonged period is for excep- 

 tional individuals or (usually) represents incomplete inanition, where some food 

 is available. Allescher's observations on Dileptus indicate that temperature is 

 an important factor, the duration period increasing from four or five days at 

 6°C. to a maximum of seven to twelve days at 15 , then decreasing to five or six 

 days at 25-30 . Death in starving Paramecium sometimes occurs suddenly, 

 by rupture of the cell-membrane, but as a rule slowly, by gradual atrophy and 

 degeneration. Death from starvation may be escaped by encystment (in Didin- 

 ium) or by conjugation or encystment (in Dileptus). 



Change in Size and Form of the Cell. — All the evidence shows a marked 

 reduction in the size of protozoa during inanition. The maintenance of the 

 original size of Noctiluca is merely apparent, the increase in peripheral vacuoles 

 masking the decrease in cytoplasm. The recorded data indicate a decrease in 

 length to about one-half of the original in Paramecium, one-fifth in Stentor and 

 one-tenth in Dileptus and Pleurotrichia. Thus in these extreme cases the volume 

 may be reduced to less than 1 per cent of the original. There are also more 

 or less marked and variable changes in form accompanying the diminution in 

 the size of the body. 



Changes in the Endoplasm. — The cytoplasmic changes at first appear chiefly 

 in the endoplasm, which becomes progressively reduced in amount and 



is 



