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THE AMERICAN NATURALIST [Vol. LI 



If we conceive these two cells in question {A^ and B2) 

 which form in Myxoholus pfeifferi (Keysselitz) the pan- 

 sporoblast membrane to divide once more and the last di- 

 vision inside the spore to be suppressed, we could have 

 the type of Sphcerospora dimorpha. 



According to Keysselitz, in Myxoholus pfei/feri each 

 of the two gametocytes together with the small cell ap- 



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proach each other and each divides up until six cells have 

 arisen. Thus we have in all cases 14 cells, two of which 

 have a different divisional capacity, for they stop dividing 

 and the big cells form all the other cells which at the end 

 compose the two spores. Their later fate is indicated in 

 Fig. 5 and, though this does not concern us in this 

 discussion, we should like to emphasize the fact that two 

 gametes are always present in a certain stage of spore 

 development. We are convinced that the cells and 

 represent genetically in the pansporoblastic forms that 

 cell formation which in all monosporous, disporous and 

 polysporous species gives rise to the spore membrane 

 itself (Figs. 1 to 4). These cells or their nuclei were 

 observed by Keysselitz, Parisi, Lo Giudice, Auerbach 

 {Henneguya psorospermica), Georgevitch, and with cer- 



