THE MYCETOZOA 



In the Physaraceae the lime is aggregated in the sporangium in 

 the form of granules ; but in the Didymiaceae, though, as in other 

 Calcarineae, granular in the plasmodium stage, it assumes, when 

 separating from the maturing sporangium, a crystalline form, being 

 deposited on the sporangium wall either in clusters of crystals 

 (Didymium and Spumaria, Fig. 13, g) or in discs with a radiating 

 arrangement (Lepidoderma, Fig. 13, /t). It is clear that in this 

 process the lime must be in a state of solution as it passes through 

 the sporangium walls. 



The spores vary in diameter from 3-5 yu, (in Tubulina stipitata) to 

 16-20 /x (in Licea pusilla) ; and the size is generally approximately 

 uniform in each species. The surface may be smooth, tuberculated, 



G 



o 



FIG. 15. 



a, sporangia of Trichia varia, x 15 ; 6, one of the capillitium threads ; c, spores, x 160 ; <?, 

 a spore of Hcmitrichia chrysospora, x nearly 600 ; c, sporangia of Arcyria incarnata ; in one the 

 sporangium wall lias broken and the capillitium has expanded, in another the empty base 

 alone remains, x 16 ; / and g, capillitium and spores of A. punicea, x 160. (a, d, and e, after 

 A. Lister, 18.) 



or reticulated (Fig. 15, d) ; and the sculpture may be absent from 

 one side of a spore, a peculiarity generally associated with the 

 arrangement of the spores in clusters. 



Aethalia and Plasmodwcarps. In several species of Mycetozoa 

 the sporangia, instead of standing apart, are more or less closely 

 fused to form large compound bodies known as Aethalia, which 

 present characteristic features of shape and structure. The identity 

 of the individual sporangia may remain obvious or be entirely lost 

 in the mature aethalia, but in the course of their development their 

 compound nature is usually evident. 



In many cases (Fuligo, Fig. 16, Iteticularia, Lycogala) the proto- 

 plasm Avithdraws from the peripheral portions of the sporangia, the 

 walls of which collapse in consequence and together form a cortical 

 layer, and a similar withdrawal of protoplasm from the basal 



