412 THE CONTRACTILE VACUOLE 



Scarth and Lloyd (1927) claim that the vacuolar wall arises from the 

 "kinoplasm" of Strasburger. They observed a reciprocal quantitative re- 

 lation between kinoplasm and mitochondria. The activity of kinoplasm 

 resembles that of lecithin, which is abundant in mitochondria. On the 

 basis of this resemblance, they conclude that water at least may accumu- 

 late in the vacuoles without the visible interaction of any other struc- 

 ture. 



The observations and opinions reported in the foregoing pages, while 

 somewhat contradictory at times, point to two general conclusions con- 

 cerning the origin of contractile vacuoles. First, in the great majority 

 of forms, perhaps in all forms, fluid reaches the contractile vacuole 

 through the fusion of small vesicles, or accessory vacuoles, with the con- 

 tractile vacuole or its filling canals. The vesicles arise within what often 

 appears to be the wall of the vacuole; the accessory vacuoles usually 

 originate at a greater or less distance from the contractile vacuole, and 

 coalesce to form the latter. Second, vesicles originate within walls of 

 vacuoles which have been shown in many instances to be granular in 

 nature or to be intimately associated with granules; accessory vacuoles 

 have been reported by various authors as originating among granules 

 which may be closely associated with the vacuole, or occasionally re- 

 moved some distance from it. Thus it appears that in spite of their great 

 variety of shapes and general appearances under the microscope, con- 

 tractile vacuoles originate in a remarkably similar manner in all forms 

 so far investigated with this problem in mind. 



In certain instances authors have reported the absence of granules in 

 the vicinity of the contractile vacuole, and from this have concluded that 

 granules are not concerned in the origin of vacuoles. In this connection 

 it must be remembered that in certain forms, e.g., Euplotes, some of 

 the Ophryoscolecidae, and apparently in others as well, the accessory 

 vacuoles which ultimately give rise to the contractile vacuole originate 

 at some distance from the ultimate site of the final vacuole. Also, gran- 

 ules frequently are visible only after osmium or silver impregnation. 

 Keeping in mind the greater vulnerability of negative evidence, one is 

 justified in the thought that perhaps a reexamination of organisms for 

 which the absence of granules in the vicinity of the vacuole has been re- 

 ported, may reveal the presence of granules in other parts of the body, 

 either scattered or in aggregates. Such scattered granules, which are known 



