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Scientific Proceedings (132) 



purate only on being evaporated to complete dryness, a pro- 

 cedure obviously so drastic as to render it inapplicable in the 

 case of protozoan cells where it is essential to preserve the 

 vacuole and its contents intact. Mass cultures so treated leave 

 a lemon yellow residue. 



Cultures of Paramecium, concentrated by brief centrifuging, 

 and subjected to the same test also offer only negative results. 

 Examination of the vacuolar fluid is precluded in these forms 

 by the contraction of the vacuoles during the process of fixation. 



This would indicate, therefore, either that uric acid is not an 

 end product of the katabolic activity of these protozoa, or that 

 the murexide test is not sufficiently sensitive to give a satisfac- 

 tory optical reaction in this case. In view of the latter possi- 

 bility, other and more specific methods for determining the pres- 

 ence of uric acid in minute quantities, are being applied at the 

 present time. 



The complete paper will appear in the Journal of Experimental 

 Zoology. 



233 (2193) 



Studies on the contractile vacuoles of Amoeba verrucosa and 

 Paramecium caudatum. 



By RUTH B. HOWLAND (by invitation). 



[From Cornell University Medical School, New York City] 



The contractile vacuole of Amoeba verrucosa is formed by 

 the union of a variable number of lesser globules. Subsequent 

 to each contraction a new series of contributary globules may 

 appear in the same location as the preceding vacuole, but this is 

 not invariably the case. Random formation of new vacuoles is 

 common, either at some distance from the original organelle, 

 or close by. The walls of two functioning vacuoles may lie in 

 contact for some time without confluence. 



The wall of the vacuole is easily indented with a blunt micro- 

 needle. A sharp-pointed microneedle will induce artificial systole 

 by perforation of the wall of the vacuole. 



