No. 612] MYXOSPORIDIAN LIFE CYCLE 725 



zew's presentation differs from that of the other author 

 in one important point. The cells A and B in Fig. 2 

 are said to be in Cerafomyxa drepanopsetta the prod-' 

 ucts of a fusion of two cells. The reader has but to change 

 the lettering of A in AC and of B in BC to see that the 

 two'copulas undergo changes identical with the two single 

 cells in Sphcurospora dimorplia. Except this one point 

 of difference— the beginning of spore formation— we note 

 that the late division of the membrane-forming cell, the 

 identical number of cells in each spore and the independ- 

 ence of each spore in the mj^osporidian body characterize 

 both species of Cerafomyxa (Awerinzew and Mavor) and 

 Sphmrospora (Davis). It appears highly improbable that 

 in two different species of CeratomyxidcB the basis of 

 spore formation should be a copula (Awerinzew) or an 

 univalent nucleus (Mavor). 



Summarizing the known description of spore formation 

 of those myxosporidia, in which each spore is formed in- 

 dependently of the other in the somatic body, and where 

 no pansporoblast exists, we can demonstrate the following 

 uniform features in all investigated forms. 



1. Six cells or nuclei are used for the formation of each 

 spore, when two polar capsules are present ; eight, when 

 four polar capsules are present. 



2. The cells which form the spore membrane have a 

 similar origin and are distinguished by the independence 

 in which these cells develop as compared with the other 

 constituents of the spore. Their mother cell is lying in a 

 resting stage till the division of the gametocjie is finished, 

 as described by Davis for Sphcerospora dimorpha, and by 

 Awerinzew for Ceratomyxa drepanopsettce. 



In Myxidiwn sp., where, according to the investiga- 

 tions of Awerinzew, either one, two or three spores are 

 lying independently in the myxosporidian body, there is 

 a very late division of the cell, the divisional products of 

 which form the spore membrane as recorded by this author 

 (Fig. 3). Here the one gametocyte divides into two 

 cells, one of which by a late di\dsion gives rise to the two- 



