44 



THE MYCETOZOA 



the number of fused amoebulae increases, direct observation of the 

 behaviour of the nuclei is, owing to their small size and the bulk 

 and movements of the protoplasm, increasingly difficult, and soon 

 becomes impossible. 



Before describing the plasmodia in detail, it may be briefly 

 stated that they are masses of naked protoplasm of indefinite size, 

 containing numerous small nuclei. As de Bary discovered, they 

 are capable, under certain conditions, of passing into a passive 

 condition known as the Sclerotium, in which the protoplasm is 

 aggregated in cysts (Fig. 8), which together form a mass of horn- 

 like consistency. On the return of favourable conditions the 

 plasmodium resumes the active condition. 



The mode of life of the plasmodium differs in different species, 



FIG. 6. 

 Part of a plasmodium of Bailhamia ittriculans expanded over a slide, x S. 



some (as in most of the Trichiaceae and Arcyriaceae) penetrating 

 the interstices of dead wood, others (as of most species of Craterium 

 and Didymium) living among heaps of decaying leaves, while one 

 species, Badlmmia utricularis, feeds on the surface of living fungi 

 which grow from the bark of dead trees. 



The plasmodium expands over surrounding objects and moves 

 about, taking in nourishment. When exposed, it is seen by the 

 naked eye to be traversed by systems of vessel-like thickenings, the 

 main trunks of which divide and subdivide as they approach the 

 periphery, and are in free communication by the anastomosis of 

 their branches (Fig. 6). 



The border of the plasmodium in the direction towards which 

 it is moving generally consists of a continuous film of protoplasm, 

 traversed by smaller branches of the system, but in the other parts 

 the film is generally not continuous, being interrupted in the inter- 



