242 



BIOLOGY 



shell is produced around the eight sporozoites and the whole 

 cluster of eight is called a sporoblast. All of this has occurred 

 within the original cyst, which has by this time become filled 

 with a large number of these sporoblasts, each with its eight 



FIG. 112. MONOCYSTIS, SHOWING METHOD OF REPRODUCTION 



A, the full-grown animal; B, two individuals enclosed in a cyst; C, the division of the 

 nucleus into a number of parts, the protoplasm not yet divided; D, successive stages of the 

 fusion of the cells which result from division of the two animals in C; F, the cyst containing 

 numerous sporoblasts; G, shows the sporoblast breaking open to allow the spores to emerge, 

 which develop into adult animals. The stages represented in G occur only when the animal 

 reaches another earthworm. 



sporozoites within; see Fig. F. Eventually the cyst breaks 

 open, allowing the contents to escape. Later these sporcblasts 

 themselves break open and the individual sporozoites come out 

 ready to grow into new animals like the original Monocystis; 

 Fig. G. These latter stages do not occur unless the sporozoites 

 find their way into another earthworm, where they live as 

 parasites until ready to multiply again. The sporozoites are 



