EFFECT OF EXCRETION PRODUCTS OF PARAMAECIUM 561 



decolorize rosol, and he therefore concluded that carbon dioxide 

 is excreted by the organisms in quantities sufficient to be detec- 

 ted with proper reagents. The work of Barratt^^ may also be 

 mentioned in which he found that the daily carbon dioxide pro- 

 duction of Paramaecium varies between 1.3 aiid 5.3 per cent of 

 the weight of the protoplasm, the variations in amount being 

 largely due to temperature and the food supply of the animals. 



Beyond the fact that CO2 is eliminated by the infusorian cell 

 and chiefly by the contractile vacuole, there are comparatively 

 few data as to the form in which other products of katabolism 

 leave the animal. The so-called excretory granules found in 

 practically all groups of Protozoa have been quite carefully stud- 

 ied in Paramaecium. They were early supposed by Entz and 

 others, by analogy with higher forms, to represent concretions 

 similar to uric acid crystals. Schewiakoff^^ claimed, as the 

 result of a series of careful tests, that they consist of calcium ortho- 

 phosphate, and, as calcium is one of the most abundant metallic 

 elements in cells, some probability is attached to his conclusion, 

 especially since Schaudinn'-" determined the presence of calcium 

 and phosphoric acid in the excretory granules of Trichosphaerium. 

 Rhumbler,-^ however, considering the excretory granules of var- 

 ious Infusoria concluded that they consist of uric acid, and Grif- 

 fiths^^ believed that he had demonstrated by microchemical tests 

 the presence of uric acid in the contractile vacuoles of several 

 types of protozoa, including Paramaecium. 



Rossbach^s in 1872 observed that temperature affected the fre- 

 quency of the contractions of the contractile vacuole and this 

 was confirmed by Maupas--* in 1883. The French author also 

 computed the relative volume of the contractile vacuole and cell 

 of several Infusoria and determined, for example, that at a tem- 

 perature of 27° C. Paramaecium aarelia evacuates a quantity of 



18 Barratt, Zeit. f. AUgen. Physiol., Bd. 5, pp. 166-172, 1905. 



1^ Schewiakoff, Zeitschr. f.-wiss. Zool. Phys., Bd., 17, 1893. 



2»Schaudmn, Abhandl. d. k. Akad. d. Wiss., 1899. 



^1 Rhumbler, Zeitschr. f. wiss. Zoolog., 1899. 



22 Griffiths, Proc. Royal See. Edinburgh, vol. 16, 1889. 



2' Rossbach, Arb. a.d. Zool.-zoot. Inst. Wurtzburg, pp. 9-72, 1872. 



2^Maupas, Archiv. de zool. exp. et gen. (2), 1 p. 648, 1883. 



