354 H. S. DAVIS 



I believe it must occur not later than the binucleate stage. In 

 all later stages the nuclei are distinctly differentiated into vege- 

 tative and generative nuclei which are very characteristic, and 

 no trophozoites have been seen which could have been formed 

 by the division of such an individual. On the other hand there 

 is evidence that the young binucleate forms may divide, and it 

 is interesting to note that such a method of reproduction has 

 been found by Auerbach in Myxidium bergense. However, the 

 evidence of division is not conclusive, and for various reasons 

 this species furnishes very unfavorable material for the deter- 

 mination of this question. I believe it is questionable whether 

 plasmotomy as defined by Doflein, occurs normally in the di- 

 sporous Myxosporidia. The whole subject is in need of careful 

 investigation. 



Turning to the polj^sporous form we find that here, also, there 

 is practically no evidence that plasmotomy is a normal occurrence. 

 It has been observed on the slide under abnormal conditions, 

 but there is little warrant for believing the process to occur 

 normally. A few individuals were observed on the slide which 

 showed rounded processes strikingly like those described by 

 Cohn ('96) in Myxidium lieberkiihni and which he believed to 

 be a process of budding.^ As previously stated, I believe these 

 processes are abnormal; formed as a result of the pressure of 

 the overlying coverglass, and that they have no significance in 

 connection with reproduction. 



The normal method of multiplicative reproduction in the poly- 

 sporous form is, I believe, by the formation of gemmules. Tro- 

 phozoites containing gemmules were so abundant as to leave 

 no room for doubt that multiplication, by this method is rapid 

 and sufficient to account for the large number of polysporous 

 trophozoites found in many instances. 



^ Laveran and Mesnil ('02) deny that such budding occurs. They find that 

 the trophozoites formed by plasmotomy may attach themselves to the larger 

 individuals, thus giving rise to the appearance erroneously interpreted by Cohn 

 as budding. In S. dimorpha the exterior of the large trophozoites are distinctly 

 viscid and small trophozoites may become temporarily attached to them. How- 

 ever, there is no doubt that the processes shown in figure 58 are due to extrusion 

 of the ectoplasm. 



