156 PROTISTS AND DISEASE 



When nutritive material is used up, so states van Tiegham, 

 the myxamoebae converge on certain centres and become 

 apposed without fusion ; each such aggregation erects itself 

 perpendicularly, the elements climbing over one another to 

 take characteristic shape in a spore-apparatus. The long 

 plasmodial stage accompanied by growth seen in the 

 Mycetozoa is wanting in the Acrasieae. 



Spores are constituted by encapsulation of separate 



FIG. 44. DIAGRAM OF STAGES OF ACRASIEAE. 1, a, Amoebula ; 6, binary 

 division of same ; c, false plasmodium (cohesion without coalescence) ; 

 d, formation of sorus and spores. 2 } Stage in sporangium-formation 

 in the Dictyostelidae massed amoebulae of which the innermost are 

 transformed into a skeleton up which the rest climb. 



amoebulae in the aggregations. They are held together by 

 glutinous material. There is no sporangia! membrane like 

 that of the endosporous Mycetozoa ; van Tiegham compares 

 them in this respect to the exosporous Mycetozoon, Cera- 

 tiomyxa, Fig. 45, 6 to 11. 



In unfavourable surroundings the myxamoebae form 

 protection- cysts, which may be two or even three-fold in 

 Guttulina. 



