GENERAL PHYSIOLOGY 171 



contains water-soluble katabolic excretory substances such as CO2 

 and nitrogenous waste, positive evidence for which is supplied by 

 Rowland. This indeed was admitted by Degen although he 

 obtained no evidence of the nature of the substances excreted. He 

 saw in the membrane of the vacuole the possibility of an excretory 

 mechanism. The actual existence of such a membrane, however, 

 is still in dispute, indeed the majority of investigators deny its 

 existence (Biitschli, l{huml)Ier, Schewiakoft', Taylor). Others, 

 however, give evidence to show that a true membrane, although 

 very delicate, is actually present. Rowland (1924, 1) for example, 

 by micro-dissection methods has been able to remove the contractile 

 vacuoles of Amoeba rerrvcosa and of Paramecium caudahim after 

 which they retain their integrity for considerable periods as free 

 vacuoles in the surrounding water. She also has jjinictured the 

 vacuole with needles while in the endoplasm, causing the expulsion 

 of its contents into the surrounding endoplasm and resulting in 

 the wrinkling of the vacuole membrane. Xassonov (1924) also not 

 only demonstrates the presence of a meml^rane in various types 

 (Paramecium candatvm, Lionofus folium, Nassula Jateritia, Cam- 

 panella V7ubellaria , V art icell idee, and Chilomonas iiaramecium) but 

 by use of fixation methods employed for demonstrating the Golgi 

 apparatus in metazoan cells, comes to the conclusion that the 

 membrane of the contractile vacuole is the homologue of the Golgi 

 apparatus. This, in Metazoa, he had earlier (Nassonov, 1923) iden- 

 tified as an organoid intimately bound up with secretory activities 

 of the cell (see also Bowen). In different Protozoa the contrac- 

 tile vacuole, which he unhesitatingl\- calls an excretory apparatus 

 with a definite lipoid membrane, is variousl\' complicated, from a 

 simple vesicle with osmiophilic membrane in forms like Chilomonas 

 'Paramecium (Fig. 85, B), to complex aggregations of vesicle and 

 canals as in Paramecium (Fig. 85, A, C). In the latter case the 

 canals appear to contain the material by activity of which sub- 

 stances are chemicalh' differentiated for secretion and these are 

 passed on to the vesicle through whose activity they are excreted. 

 With this work of Nassonov's, which is convincingly presented, we 

 have a very definite statement of the excretory functions of the 

 contractile \acuole and of the presence and function of the lipoid 

 membrane. In quite a modern wa\' it brings us dangerously near 

 to an Ehrenbergian conception of a kidney and bladder in Protozoa. 

 B. Irritability.— In the absence of all knowledge as to the manner 

 in which protoplasmic particles respond to stimuli of different kinds, 

 we are constrained in speaking of irritability of Protozoa, to limit 

 descriptions to aggregates of such responses as manifested through 

 movement, as energy transformed by oxidation from the poten- 

 tial or stored chemical energy-, to the active of kinetic condition. 

 But the manner in which such kinetic energy is utilized in pseudo- 



