^114 C. M. CHILD. 



to that figured by Richards for Tcenia, but after comparing the 

 results of various fixing agents I came to regard it as highly- 

 probable that the " strands of linin " were simply coagulation 

 products and therefore stated (I., p. 93) that "a distinct reticular 

 structure does not appear." Richards (p. 316) attributes to me 

 the statement that " the nuclei do not contain any definite retic- 

 ulum." Though I am not desirous of sphtting hairs this seems 

 to me a much more positive statement than that which I did 

 make. I do not know how widely different the nuclei o{ Moniezia 

 are from those of Tcenia, and while I could give figures showing 

 " strands of linin " in some of these nuclei, I am strongly skep- 

 tical, for the reasons given above, as to their representing in 

 Moniezia a real nuclear structure existing before fixation. As 

 the germ cells approach maturation the visible nuclear structure 

 undergoes alteration, as my figures show, and the non-chromatic 

 portions show more definite and constant characteristics. Rich- 

 ards in his work has apparently employed only Flemming's and 

 Zenker's fluids, both of which will, under certain conditions, 

 produce reticular structure in solutions of proteids. Since the 

 "strands of linin " were sometimes confusing in the study of the 

 nuclear membrane I often found it desirable to extract the stain 

 to such an extent that they were only slightly stained, or to em- 

 ploy fixing agents which did not show them in the resting nuclei. 

 But the chief interest centers of course about the occurrence 

 or non-occurrence of amitosis in the germ cycle. It is evident 

 that if all the nuclei which are included in a given proglottid 

 arise, or may under certain conditions arise, in the neck-region 

 by amitotic division the germ cells must arise from nuclei which 

 have previously divided amitotically. This conclusion is, how- 

 ever, open to the objection that since we cannot be certain that 

 every individual nucleus in the neck-region has divided ami- 

 totically, it may be possible that the nuclei of the germ cycle 

 have not so divided. 'This objection is actually of little force, for 

 there are probably not enough parenchymal nuclei in the neck- 

 region at any one time to give rise even to all the mother germ 

 cells which appear. Nevertheless this objection must be reckoned 

 with and I should not for a moment maintain that the amitotic 

 division in the neck-region constitutes absolute proof of the 

 occurrence of amitosis in the germ cycle. 



