METHOD OF CELL DIVISION IN MONIEZIA. 14! 



that this easily lies within the limits of observational error. 

 These cases may be considered as evidences of recent division; 

 they are not, however, distinctive of either direct or indirect 

 division. If there were abundant evidence of the former they 

 would be regarded as adding to it. On the other hand, if spindles 

 were very numerous this arrangement in pairs would be looked 

 upon as the final stage in the division of the cells by mitosis. 

 Cases of juxtaposition of nuclei are seen in Figs. 2, 12 and 17. 



One may occasionally see in some sections a few nuclei darker 

 than their neighbors (Fig. 18) scattered among the pre-oogonia. 

 They have no visible significance; they differ from other nuclei 

 only in being darker. I have never seen one half of a nucleus 

 darker than the other. I may here add that there is never a 

 dark body, a "Nebendotter" occupying a portion of an ovum 

 as in Tfsnia. 



Rarely, indeed, does one find constricted nuclei in my prepara- 

 tions. Shrunken and irregular nuclei artifacts occur; strands 

 of linin across a nucleus often resemble the formation of a plate 

 (as in Figs. 41 and 42) ; the edges of adjacent nuclei overlap and 

 sometimes the overlapping parts are so thin that the true con- 

 dition is not at first apparent; but the various stages of plate 

 formation, constriction, etc., and especially of "endogenous" 

 division as set forth by Child I have never seen. One does, 

 however, occasionally find a dumb-bell-shaped nucleus; but so 

 infrequent are they that I am unable to determine any signifi- 

 cance for them. 



I find myself, therefore, unable to confirm Child's conclusions 

 for the various reasons given. His position, however, that the 

 "relative frequency of mitosis and amitosis in certain species, 

 and even in single individuals may vary greatly according to 

 conditions" ('10, p. 116) is an unassailable one with our present 

 data. 



The Oogonial Period. From the disc-like anlage on the ventral 

 side of the proglottid upward projections or follicles develop and 

 give to the ovary its characteristic form. 1 About the time of full 

 development an enveloping membrane appears probably as a 

 differentiation of the surrounding parenchyma. For the female 



x Cf. Photomicrograph III. 



