408 THE CONTRACTILE VACUOLE 



lecting pusule with daughter vacuoles and numerous accessory vacuoles 

 were observed in Phalacroma sp. In Goniodoma sp. there were, besides 

 a sac pusule, a collecting pusule with daughter pusules and an accessory 

 vacuole. Only one large pusule was noted in Ceratium hirnndineUa. Ir^ 

 both orders of flagellates Haye believes that emptying of accessory vacu- 

 oles is accomplished by diffusion through the walls into the contractile 

 vacuole, rather than by coalescence with it. 



Hall (1930b) found that in Menoidium, stained according to the Da 



\ Fano silver method, the contractile vacuole is formed by the fusion of 

 several smaller vacuoles arising near the gullet. 



The mode of origin of contractile vacuoles has been studied in a 

 greater variety of ciliates than in either rhizopods or flagellates, and in- 

 formation on this subject is proportionally more abundant. Taylor 

 (1923) observed in Euplotes that the vacuole (VJ, in its final form 

 immediately before contraction, is the result of the fusion of several 

 smaller vacuoles, and that these smaller vacuoles (designated as group 

 V2) in turn are formed by the fusion of still smaller vacuoles (group 

 V3) . The smallest vacuoles in the series are thought to arise as the result 

 of the dissolving of granules, or to arise de novo. Thus Taylor suggests 

 granules as a possible source of vacuolar fluid, and he observed formation 

 of the vacuole by the fusion of several small accessory vacuoles. King 

 ( 1933) , who studied Euplotes after impregnation with osmic acid, found 



.that the smallest visible accessory vacuoles (Vg) have their origin at the 

 distal ends of a very large number of collecting canals, located just under 

 the ectoplasm on the dorsal surface of the ciliate. These canals radiate 

 like a sun-burst from the vicinity of the vacuoles, and seem to end blindly 

 in the protoplasm of the organism. These canals have a diameter of ap- 

 proximately 0.5 micron at their distal ends, and become relatively much 

 narrower as they pass away from the region of the vacuoles. The canals 

 are not visible in living organisms, but may be clearly demonstrated by 

 proper impregnation with osmic acid. On the basis of information now 

 available, it is difficult to tell whether the canals described by King and 

 the granules mentioned by Taylor represent different interpretations of 

 the same structures, observed under different conditions, or whether the 

 canals merely provide a means for the transport of fluids which have 

 originated in more distant parts of the body as a result of the activity 

 of granules. 



