Metazoa and Metaphyta. 67 



may be looked upon as in reality a multicellular stage in the 

 life-history of a unicellular organism ; but that condition is 

 retained as the permanent adult form only in one or 

 two aberrant groups of plants (fig. 15). In the sponge 

 group and allied forms amongst animals the plasmodial 

 stage is permanently exemplified ; it also appears in ab- 



Fio. 15. PLASMODIUM OF Didymium leucopus. (Sachs.) 



normal (diseased) cells and, in certain cases also, normally 

 in the higher Metazoa (fig. 14). In disease the ciliated cells 

 are those which most commonly, losing their cilia, become 

 plasmodial. Such collections of diseased cells are plasmodia 

 in which the nuclei of the constituent cells are still visible, 



F 2 



