102 PROTOPLASM 



and for the most part slightly sinuous, line from the con- 

 tiguous striated portion. The oral nipple is formed from 

 this granulated portion and from the neighbouring thicker 

 striated portion of the shell, which, at the time when the 

 protoplasm forces its way out and widens the oral opening, 

 becomes raised up and pushed apart. I believe that the 

 peculiar nature of the opening serves to supply an elastic 

 closing apparatus, which of itself closes up the aperture 

 again after the protoplasm has flowed back. 



As a rule the opening has sticking to it a mass greater 

 or less of various kinds of detritus, which at times may even 

 considerably exceed the animal in circumference. This 

 lump of dirt consists of particles of the most varied sorts, 

 which the Protozoon has collected together by its pseudo- 

 podia, and has gathered up in front of the oral aperture. 

 Since it can be not infrequently observed that pseud opodia 

 apparently take their origin direct from the edge of this 

 lump, I regard it as certain that the protoplasm extends 

 between the particles of the mass, holds it together, and 

 makes use of it as food. This circumstance is a great 

 hindrance to the investigation, since the aperture, and 

 especially the protoplasm issuing from it, is usually quite 

 covered by the dirt. If the mass be removed cautiously 

 the aperture usually closes at once, and even after keeping 

 the animal for a long time new pseudopodia are only rarely 

 sent out. 



The protoplasm which fills the shell is completely 

 opaque, since it is packed full of large brown bodies 

 (Fig. 1, c) which long ago attracted the attention of M. 

 Schultze on account of their great resistance to various 

 reagents. 



In specimens in which it was possible to watch the 

 pseudopodia being sent out, the process observable was as 

 follows. Through the more or less widely opened aperture a 

 mass of protoplasm emerges which quite fills it, and which has 

 a structure very distinctly composed of elongate meshes giving 

 the appearance of longitudinal fibrils. This is by no means 

 a bunch of pseudopodia projecting from the oral aperture, 

 as M. Schultze described it, but a continuous mass, with a 



