116 ZOOLOGY 



which were shown to be continuous with those of the reservoir 

 (Fig. 58, A). In systole the impregnated wall of the reservoir was 

 small and darkly stained and the canal impregnation reduced 

 almost to rods. In diastole, however, the canals in section 

 appeared as rings and the reservoir was large and lightly im- 

 pregnated. 



In Chilomonas paramoecium the simple reservoir was deeply 

 stained round its periphery, although the point of opening into 

 the pharynx was free from impregnation (Fig. 58, B). 



The impregnation is in all cases very definite, limited and 

 intense. Nassonov concluded that the " membrane " so impreg- 

 nated secreted (or excreted) the fluid found in the contractile 

 vacuoles at diastole. 



His own work on the connection between secretion and the Golgi 

 apparatus of the Metazoa, taken together with this new example, 

 leads him to homologise the walls of the contractile vacuoles of the 

 Protozoa with the metazoan Golgi apparatus. This is based not 

 merely upon similarities of staining reactions, but also upon the 

 general morphology and, most important of all, upon similar func- 

 tion. As regards the morphology a general resemblance will be 

 seen between the incomplete sphere of the impregnated wall of 

 the contractile vacuole and the form of the Golgi during acrosome 

 formation and during cell secretory activity. Homologies based 

 on morphology of the Golgi apparatus cannot be pressed too far, 

 as we have seen that the present view does not stress the import- 

 ance of the actual morphological form. 



In respect of the functions it is quite evident from Nassonov's 

 own preliminary work (and Bowen's later very exhaustive survey) 

 of the relation of the Golgi apparatus in gland cells to secretory 

 activity that secretion of various granules or vacuoles is a common 

 function of the Golgi apparatus. The excretion of fluid into a con- 

 tractile vacuole is an exactly comparable process. In fact it may 

 be acknowledged that secretion and excretion are frequently 

 identical and the choice of the terms depends upon the point of 

 view. Nassonov therefore feels justified in asserting the homology 

 outlined above. 



Objections were raised against this hypothesis chiefly upon the 



