558 MAVOR. 



einem einkernigen durcli karyokinetische Teilimg des urspriinglichen 

 Kernes; die beiden sich auf diese Weise bildenden Kerne sind einander 

 voUig gleichwertig vind in niorpliologischer Hinsicht in keiner Weise 

 voneinander verschieden." 



The two nuclei in the l^inucleate stage of the myxosporidium of C. 

 acadiensis are not only different in size but they also show a different 

 staining reaction. As one of these nuclei, the more faintly staining, 

 probably gives rise to the two trophonuclei and the other, the more 

 tleeply staining, to the nuclei of the sporoblasts, there are already at 

 the binucleate stage two kinds of nuclei. This condition was not 

 found by Awerinzew until the stage with four nuclei was reached. 



The fact that the two nuclei of the myxosporidium ha\e, the one a 

 trophic and the other a propagative function, makes it improbable 

 that the binucleated myxosporidium is formed by the fusion of two 

 uninucleated individuals as has been supposed by some authors. A 

 fusion at this stage is rendered still more improbable by the occurrence 

 of stages in the division of the single nucleus. If a fusion of two myxo- 

 sporidia really takes place in the life-history, it would seem more 

 probable that it occurs between two binucleate individuals, each pos- 

 sessing a vegetative and a propagative nucleus. Such a fusion between 

 binucleate individuals would be an interesting parallel to the condi- 

 tions found by Keysselitz (:08) and Schroder (: 10), where two pairs 

 of cells come together to form a pansporoblast. Of the four cells 

 found by these authors, one from each pair forms the en\elope and 

 takes no part in the formation of the sporoblasts, while the other two 

 form the two sporoblasts. The nuclei of the two cells which form the 

 envelope could then be compared with the two trophonuclei of C. 

 acadiensis, while the two cells which form the sporoblasts could be 

 compared with the two sporoblast-mother-cells of C. acadiensis. The 

 writer has, however, no evidence that such a fusion of myxosporidia 

 occurs, and indeed the conditions in the stage with three nuclei is 

 strong evidence against this. 



The two accounts (Awerinzew's and my own) agree in the main 

 for the stage with four nuclei, there being in the myxosporidium of 

 both C. acadiensis and C. drepanopsettae two trophic nuclei and two 

 nuclei of propagative function. 



The formation of microgametes and macrogametes and their 

 subsequent fusion to form zygotes, I have not observed. It must 

 be said, however, that the small size of the object and the close prox- 

 imity of the nuclei renders the observation of any such phenomena very 

 difficult. 



