CYTOLOGY OF THE MYXOMYCETES. 79 



appearance of basophilic chromatic material. The ground sub- 

 stance of the protoplasm presents a sort of flocculent appearance, 

 being denser in some regions than in others. The first indication 

 that spore formation is taking place is to be seen in the clumping 

 of the mitochondria. All the mitochondria are in the form of 

 spherules of fairly uniform size. They stain with equal in- 

 tensity with iron hematoxylin. The differences in shade illus- 

 trated are indicative of perspective only. Soon the little clumps 

 of mitochondria become surrounded by a membrane, the first 

 spore membrane, which stains only faintly with iron hematox- 

 ylin. Traces of nuclei can be seen in some of these early spores. 

 Spore formation proceeds from a definite center so that it is 

 possible to see many stages in a small area. Fig. 8 is taken 

 through such an area, the early stages being above and the later 

 stages below. In certain other Myxomycetes, however, spore 

 formation is said to take place simultaneously throughout the 

 whole sporangium. 



Rather more advanced stages in Fuligo septica are shown in 

 Figs. 7 and 9. Here all the spores are well formed and discrete 

 and surrounded by membranes. The nuclei have reappeared. 

 They are spherical and stain diffusely. It is difficult to dis- 

 tinguish any nucleoli within them, since they are of about the 

 same size as the mitochondria. There is no apparent change in 

 the mitochondria. The ground substance of the protoplasm 

 presents the same flocculent appearance with a marked tendency 

 toward the production of vacuoles in some of the spores. 



Very profound changes now take place. In Fuligo septica 

 (Fig. 10) the spores lose every trace of their membranes and de- 

 generate into naked, nucleated masses of protoplasm which are 

 distinctly smaller than in the preceding stage. They also lose 

 their spherical or oval shape and become often quite angular. 

 Their nuclei stain so intensely with iron hematoxylin that it is 

 difficult to make out any structure in them. The ground sub- 

 stance is more homogeneous and stains diffusely and evenly. 

 The appearance of the mitochondria has completely changed. 

 Instead of occurring in the form of large spherules they are now 

 considerably smaller, rod-like and sometimes almost filamentous. 

 They often clump about the nuclei in a manner suggestive of 



