CELLULAR STRUCTURE 33 



veloped by the swelling jelly, and they may 

 even entirely disappear. The cell colonies 

 thus consist of motionless masses of green 

 jelly. But there is as yet very little organisa- 

 tion in such colonies. The form of the mass 

 is not constant, and a return to what may be 

 termed normal conditions of life may readily 

 lead to a complete disruption of the colony, 

 the individual cells escaping from the jelly 

 and returning to the unicellular motile condi- 

 tion which is in the main characteristic of this 

 group of algae. 



This tendency to form agglomerations of in- 

 dividual cells is carried to a far greater degree 

 of perfection in some other groups of the lower 

 algae. Thus Apiocystis Brauniana (Fig. 2), 

 an alga fairly often to be met with in ponds, 

 attached to larger algae and other objects, 

 consists of a pear-shaped mass of jelly in 

 which are scattered masses of chlorophyll- 

 containing protoplasm. The little proto- 

 plasmic spheres, which represent the living 

 part of the individual cells composing the 

 Apiocystis plant, are grouped in the more 

 peripheral parts of the gelatinous matrix 

 formed by the swelling of the common cell 

 walls. Each cell (see footnote on p. 20) is 

 furnished, like Chlamydomonas, with a pair 

 of cilia, but these have ceased to be functional, 

 for they are enclosed in a thin projection 

 of the gelatinous wall. When examined 

 attentively, it can be observed that the 

 individual cells, or protoplasts, are multiplying 



