THE MYCETOZOA 



in the relation of the spores to the supporting structures, and 



in the changes which occur 

 when the spores are hatched 

 (Fig. 18). 



The plasmodium inhabits 

 rotten wood and emerges in 

 cushion-like masses, which may 

 become honeycombed with de- 

 pressions or separate into dis- 

 tinct antler-like branches. On 

 its emergence it assumes the 

 condition of an intimately 

 anastomosing network of pro- 

 toplasmic strands distributed 

 through an abundant hyaline 

 gelatinous substance, and at 

 first exhibiting the characteristic 

 rhythmic ebb and flow seen in 

 the plasmodium of the Endo- 

 sporeae. As the definitive 

 shape is assumed, the proto- 

 plasm leaves the interior and 

 accumulates at the surface of 

 the mass, at first as a close- 

 set reticulum, and then as a continuous layer investing the 

 gelatinous substance, though with a thin covering of the latter still 

 external to it. The layer of protoplasm then separates into a- 

 mosaic of polygonal cells (Fig. 18, b), each occupied by one of the 

 nuclei of the plasmodium. The cells are at first in contact with 

 their fellows at their margins, but they now draw apart, and each 

 projects in the centre of the area which it occupied, beyond the 

 contour of the lobe on which it lies, though still covered by the 

 thin hyaline layer. As the projection increases its base becomes- 

 constricted, and finally the cell, or young spore, containing the 

 nucleus and all the protoplasm which occupied the polygonal area, 

 is raised some distance above the general surface, invested by 

 a thin covering, and supported on a slender stalk both furnished 

 by the investing layer. Each spore now assumes an elliptical 

 shape, secretes a firm colourless wall, and is ready to drop away. 1 



During the later stages of this process the gelatinous material' 

 constituting the sporophore dries, and by the time the spores are 

 ripe, forms a shrivelled, white mass of extreme tenuity (Fig. 18, a). 

 According to Famintzin and Woronin (9), who first described the 

 details of the life-history of Ceratiomyxa, the protoplasm emerges in 

 the morning and the spores are ripe within twenty-four hours. 



1 For nuclear changes during spore-formation, cp. p. 66. 



FIG. 18. 



Ceratiomyxa mucida, Schroet. a, ripe 

 sporophore, x 40 ; 6, maturing sporo- 

 phore, showing the development of the 

 spores, x about 100 ; c, ripe spore ; d, 

 hatching spore ; e-h, stages in the develop- 

 ment of the zoospores, x 800. (a and c-h 

 after A. Lister, 18 ; 6, after Famintzin and 

 Woronin, 9.) 



