562 MAYOR. 



two figures being difTerent views of the same sporoblast, no division 

 into separate capsulogenous cells could be made out in the mass of 

 protoplasm which contains the two nuclei; but in another sporoblast 

 of about the same stage (PI. I, Figs. 23, 24) a differentiation into two 

 capsulogenous cells could be seen. As compared with the conditions 

 shown in Figui-e 17 (PI. I), the nuclei of the capsulogenous cells have 

 become slightly larger, and the nuclear net does not show clearly, prob- 

 ably on account of a movement of achromatin toward the periphery 

 of the nucleus. 



The formation of the polar capsules in cells of their own was first 

 shown by Biitschli ('81), who was also the first to realize their true 

 nature. In some cases, however, the formation of the separate cells 

 occurs later in the development when the sporoblasts are already 

 formed, as in the polysporic genera Myxobolus (Keysselitz, : 08) and 

 Sphaeromyxa (Schroder :07). 



The two nuclei of the sporoplasm are seen close together on the left 

 in Figure 18 (PI. I), in the middle in Figure 23, and alone in Figure 25. 

 Henceforth these two nuclei will be called the germ-nuclei,^ since they 

 are the nuclei of the germ carried in the spore-shell. The germ-nuclei 

 have retained the size and deeply staining character they had in the 

 sporoblast represented in Fig. 17 (PI. I). A differentiation of the 

 sporoplasm into two regions corresponding to the two nuclei was not 

 seen; these nuclei were usually found close together and, indeed, 

 almost touching each other. The examination of a large number of 

 stages in the development of the sporoblast has revealed the constant 

 presence of six nuclei in every sporoblast and consequently of two 

 nuclei in the future sporoplasm. 



It seems to be a universal condition for the sporoplasm of the myxo- 

 sporidian spore to contain two germ nuclei, at least during the later 

 stages of the formation of the spore. Thelohan ('95, p. 270) writes 

 "Le protoplasma renferme toujom's deux noyaux qui sont le plus 

 souvent accoles I'un a I'autre, d'une fa^on plus ou moins etroite, de 

 telle sorte que, dans certains cas, il parait plutot avoir un noyau unique 

 un peu allonge et un peu etrangle vers sa partie moyenne." In more 

 recent years two nuclei have been demonstrated in the spores of 

 Myxol)olus (Auerbach :06), Myxidium (Auerl>ach :07), Sphaero- 

 myxa (Schroder :07), Chloromyxum (Auerbach :07), Ceratomyxa 

 (Awerinzew :09), and Zschokkella (Auerbach :09). 



7 The term "germ-nuclei" is used for the French " noyaux du sporoplasma, 

 noyaux du germe," and for the German "Kerne des Amoeboidkeims." 



