THE GENERAL PHYSIOLOGY OF THE PROTOZOA 195 



vacuoles near, and under the influence of, the nucleus. In the 

 coccidian parasite Caryotropha (p. 352), the nucleus of the parasite 

 is connected by a kind of protoplasmic canal with the nucleus of the 

 host-cell (Siedlecki, 653). In the astomatous Ciliata (p. 451) a 

 diffuse nucleus is very commonly found, probably in relation to 

 absorption of nutriment by the osmotic method. 



The process of nutrition in Protozoa may lead in some cases, 

 not to growth of the protoplasmic body directly, but to the produc- 

 tion and storage of reserve food-substances, which are precipitated 

 in the cytoplasm, and are utilized at a later period for rapid growth 

 during reproductive phases. The reserve-materials deposited in 

 this way vary considerably in nature in different cases. Examples 

 are the paramylum-grains of many flagellates ; the paraglycogen- 

 grains of gregarines and ciliates, similar in nature to glycogen, but 

 with certain distinctive reactions ; the plastinoid granules of 

 coccidia (p. 346) ; and other similar substances. In Radiolaria oil- 

 globules and albumen - spheres occur. An important substance, 

 acting apparently as reserve- material for the growth of the nucleus, 

 is volutin (p. 68). 



The effects of starvation on Protozoa have been studied by a number of 

 investigators, most recently by Lipska (173), who gives a complete bibliog- 

 raphy and resume of previous work on the subject. Lipska found that 

 Paramecium died after five to seven days, a much shorter period than allowed 

 by Walleiigren (214) and others, indicating that Lipska's methods were more 

 drastic and sources of food were more thoroughly excluded in her experiments. 

 In the first period of starvation the reserves in the endoplasm are used up, 

 first ^the food-vacuoles and their contents, then the smaller endoplasmic 

 granules. After the fourth day the animal becomes deformed. Its dimensions 

 diminish progressively, and death supervenes when it has lost half its initial 

 volume. The ectoplasm with its cilia and trichocysts undergo no change, 

 but the endoplasm loses its food-vacuoles and a part of its crystals, and 

 becomes very transparent. The macronucleus becomes enlarged and breaks 

 up into two halves. The micronucleus undergoes no change of any kind. 

 Death is preceded by a progressive enfeeblement of all functions, such as 

 movements of the cilia and pulsation of the contractile vacuoles. According 

 to Wallengren, the reactions of the Paramecium (geotaxis, thermotaxis, 

 galvanotaxis) remain normal to the last. Wallengren described an excessive 

 vacuolation of the endoplasm as the result of starvation ; but according to 

 Lipska this phenomenon is not due to starvation, but to the chemical action 

 of ammoniacal products generated by bacteria present in the infusions, and 

 does not occur if they are excluded. Other observers noted the occurrence 

 of numerous conjugations during the first few days of starvation, but Lipska 

 was unable to confirm this ; in her experiments, however, the number of 

 Paramecia placed in each tube was small, not more than ten. Paramecia 

 containing symbiotic algae were more resistant to starvation than thoso 

 without them. 



2. Respiration. By respiration in its widest sense must be under- 

 stood all processes in the organism whereby the potential energy 

 stored up in chemical compounds of high complexity is set free to 

 furnish the energy required by the organism for its vital activities. 

 This object may be effected in two ways by processes of oxidation. 



