406 THE CONTRACTILE VACUOLE 



Mast (1926) agrees with Metcalf concerning the frequent presence 

 of granules around the vacuole, but does not interpret this as indicating 

 a physiological association between them. This opinion is based on his 

 having observed vacuoles functioning perfectly normally without the 

 presence of a single granule in the immediate vicinity of the vacuole. 

 To these granules Mast applies the name "beta granules," to distinguish 

 them from others of a different nature which are also present in the 

 cytoplasm. Mast and Doyle (1935) reinvestigated the relationship be- 

 tween granules and vacuole. By centrifuging amoebae it is possible to 

 cause stratification of various cytoplasmic constituents. Organisms treated 

 in such a manner can be operated on so as to remove all or any desired 

 portion of almost any one of the constituents, including these granules. 

 It was found by Mast and Doyle that removal of all or most of the gran- 

 ules resulted in the death of the organism. Removal of fewer granules 

 caused a decrease in pulsation frequency of the vacuole, which was di- 

 rectly proportional to the relative number of granules removed; that is, 

 pulsation frequency was found to be directly proportional to the number 

 of granules remaining. Removal of the contractile vacuole alone resulted 

 in the prompt formation of another. Concerning this same question, 

 Mast (1938, p. 312) more recently states : 



The beta granules around the contractile vacuole vary greatly in number 

 and the layer of substance in which they are embedded varies greatly in 

 thickness, without any apparent variation in the function of the vacuole. 

 These facts indicate that neither the granules nor the layer of substance is 

 involved in the function of the contractile vacuole, at least not directly. 



Howland (1924a) found that there is no concentration of granules 

 on the surface of the vacuole in Amoeba verrucosa, but she considers 

 it likely that the vacuole arises from the coalescing of small hyaline 

 globules, which in turn are derived from the dissolving of granules. 

 In any case, Howland traces the ultimate origin of the vacuole back to 

 granules in somewhat the same manner that Metcalf does, although in 

 A. verrucosa these granules are probably dispersed throughout the cyto- 

 plasm. On the other hand, Haye (1930) found in fixed and stained 

 preparations of A. vers pert iUo essentially the same relationship between 

 granules and vacuole as described by Metcalf and later by Mast; that is, 

 the filled vacuole is more or less covered by granules, and after systole 

 the new vacuole arises in the midst of these granules. 



