ON PELOMTXA VIRIDIS. 363 



scribed as highly vesicular, and Gruber/ in speaking of 

 P. villosa, which he found in Germany, says, " Zunachst 

 fallen die zahlreichen Flilssigkeitsvacuolen ins Auge, welcher 

 den grossten Bestandtheil des Korpers ausraachen und dem- 

 selben ein Schaumiges Aussehen verleihen. Diese Vacuolen, 

 die von wechselnden Umfange Sind, liegen eingebettet in 

 dem homogenen Plasma, welches mehr oder weniger feine 

 Scheidewander zwischen ihnen bildet, ahnlich eine Intercellu- 

 larsubstanz zwischen den einzelnen Zellen eines Gewebes." 



I think it probable that in these forms we have both vacuoles 

 and vesicles, but as the vesicles are filled with colourless 

 substance no distinction has been drawn between them. It 

 will be interesting to re-examine these forms to ascertain if 

 from the relative size and frequency any distinction can be 

 drawn. The importance of the question lies in this, that the 

 vesicles have probably an intimate relation to the structure of 

 the protoplasm, and possibly to the production of amoeboid 

 movements ; while the vacuoles vary from time to time in size 

 and number, and have nothing to do with the ultimate structure 

 of the protoplasm. 



Fig. 6 represents a fragment of the protoplasm in a specimen 

 which was deeply stained with osmic acid. At x is seen pro- 

 jecting at the surface a small portion of the hyaline protoplasm, 

 devoid of all contents, stained brown and rendered granular by 

 the osmic acid. The rest of the drawing shows the vesicles 

 once occupied by the chlorophyllogenous substance bounded 

 by the protoplasm. The chlorophyll has been dissolved, but 

 whether any substance now remains in the vesicles I cannot 

 determine ; there is nothing which is stained by osmic acid. 

 With all other fixing reagents which I have used the vesicular 

 structure disappears. 



The protoplasm of P. viridis appears then to be perfectly 

 homogeneous, and small portions of it may at times be observed 

 at the periphery of the organism free from all contents, but the 

 great mass of it forms a mere scaffolding for the numerous 

 vesicles, and is, moreover, densely packed with bacteria 



1 ' Zeit. f. w. Zool.,' Bd. xli, p. 189. 



