THE CONTRACTILE VACUOLE 407 



Hall (1930a) studied the cytoplasmic inclusions in Trichamoeba after 

 osmic and silver impregnation. In a few instances he observed the adher- 

 ence of blackened globules to the outer surfaces of vacuoles. At first 

 glance these appeared to be vacuoles with heavily impregnated walls, 

 but close observation revealed the granular or globular nature of the 

 blackened material. 



It must be remembered that these granules are not confined to the im- 

 mediate vicinity of the contractile vacuole, but usually are scattered 

 throughout the entire cytoplasm as well. If the origin of the vacuole is 

 associated with and dependent on the presence of these granules, then one 

 would expect other parts of the organism to be at least potentially capable 

 of giving rise to vacuoles, since some granules are present in other 

 parts. That such a phenomenon actually occurs in Amoeba has been ob- 

 served by various authors, among whom are Day (1927), as well as 

 Howland and Mast and Doyle. In this connection it is interesting to note 

 that Dimitrowa (1928) was able to induce formation of extra vacuoles 

 in Paramecium caudatum by interfering mechanically with the normal 

 function of those already present. These extra vacuoles usually appeared 

 to be entirely normal, although in a few instances there were no radial 

 canals. The customary number of vacuoles was restored at fission by 

 failure of the organism to form new ones if two extra ones had been in- 

 duced, or by the formation of one new vacuole if only one had been in- 

 duced artificially. In the event that there were three extra vacuoles, one 

 daughter cell received three and formed a single new one when it in turn 

 divided. 



Haye (1930) investigated eight species from two orders of flagellates. 

 In Phacus pleuronectes he found that the walls of contractile vacuoles 

 contain lipoid granules which are arranged in a net-like fashion. In 

 Euglena piscijormis and Tracbelomonas hispida the surfaces of both the 

 reservoir and the vacuoles show a granular structure. In Pevidinium 

 ste'mii no granules were observed, nor were accessory vacuoles seen, ex- 

 cept in organisms obtained from a laboratory aquarium in which con- 

 ditions were thought to have been abnormal. A differentiated plasma 

 zone, reminding one of the "excretory plasma" of fresh-water Protozoa, 

 was noted around the pusule. In the wall of the pusule of P. divergens 

 were observed lipoid granules similar to those in the wall of the contrac- 

 tile vacuole of fresh-water Protozoa. Besides the two sac pusules, a col- 



