362 ALFRED GIBBS BOURNE. 



The vesicles vary very little in size, being always about 

 ^o\q inch in diameter. 



The vacuoles, on the other hand, vary greatly in size, some 

 being almost as small as the vesicles, vrhile others attain five 

 or six times that diameter. 



No distinction has, as far as I am aware, been hitherto drawn 

 between vacuole and vesicle in any so-called 'Wesicular'^ or 

 '' vacuolised " protoplasm. 



Biitschli,^ writing ten years ago, says of non-contractile 

 vacuoles, *' Seltener hingegen wird ihre Zahl so betrachtlich, 

 dass das sie trenneude Plasma nur noch ein Maschenwerk von 

 Scheidewauden zwischen ihnen herstellt, das Plasma eine 

 schaumige oder alveolare Beschaffenheit annimmt. Ein 

 derartiges Verhalten begegnet uns z. b. gewohnlich bei 

 Pelomyxa, auch bei gewissen Amoben tritt ahnliches mehr 

 oder weniger deutlich hervor." 



Of Biitschli's most recent views 1 can only judge from M. 

 Yves Delage's^ note on the models of protoplasm with which 

 Biitschli has been recently experimenting, and if I understand 

 rightly in, for instance, the soap and xylol model, the plasma 

 (Biitschli) is represented by the soap and the chylema (Stras- 

 burger) by the xylol. So that the contents of both vacuole 

 and vesicle would be termed chylema, but there is no word 

 as to the possibility of the chylema being other than a single 

 substance. 



Now, in P. viridis, two distinct substances take the place 

 of the xylol of Biitschli's model, the contents of the vacuoles 

 and those of the vesicles, and were it not for the presence of 

 the chlorophyll in one of them these would not be optically 

 distinguishable one from the other. 



Two species of Pelomyxa have been hitherto described, 

 P. palustris, Greef,^ and P. villosa (Amoeba villosa), 

 Leidy.^ The protoplasm of both these species has been de- 



' Bronn, ' Protozoa,' p. 101. 



■^ ' Arch. -Zool. Experiinentale,' 1889. 



•' 'Arch, f, mikr. Anatomie,' Bd. x, 1874. 



* 'Fresh-water Rhizopods of North America,' Washington, 1871). 



