288 C. M. CHILD. 



Richards that the region of greatest proliferation is the periph- 

 ery of the primordium. Such a conclusion fails, it seems to 

 me, to take account < >f all the observed facts. The great number, 

 the very small sixe, the crowded condition of the nuclei, the 

 relatively small amount or cytoplasm and the very frequent 

 occurrence of apparent amitoses force me to maintain my original 

 position, that the central region of the primordium is a region 

 of more rapid proliferation than the peripheral. In connection 

 with this point I have evidence from various species that in 

 regions of more rapid proliferation amitosis is more frequent, 

 while in regions of slower proliferation mitosis may be the chief 

 or only method of division. 



On p. 150 Richards states that "the method of cell multi- 

 plication in the female sex ducts of Moniezia cannot at the present 

 time be positively stated." Here evidently the author has lost 

 faith to some extent in his own argument, for the conditions in 

 the ducts are not essentially different, so far as observation 

 shows, from those in the primordia of the gonads themselves. 



Of the possibility of observational error (Richards, 'n, pp. 

 140, 141, etc.) no one can be more keenly aware than myself. 

 I can only state again that I believe that I have used every pre- 

 caution possible in direct observation of fixed material. I have 

 often spent hours on a single case with the most careful focusing, 

 changes of illumination with the aid of diaphragm and mirror 

 and the alternating use of artificial light and sky light with and 

 without color screen. I'ntil Richards can show that he- has 

 taken at least equal precautions before concluding that direct 

 division is absent, he lays himself open to the charge of error 

 or superficial observation. 



As regards the difficulty of observation in the small and 

 often crowded nuclei of cestodes, a point which Richards em- 

 phasized in his earlier paper (Richards, '09), it is of course true 

 that the nuclei are small and often crowded, but if one devotes 

 sufficient time and care to the matter it is possible to find nuclei 

 which show apparent direct division with almost diagrammatic 

 clearness and I have seen many such, both in his material ami 

 in my own. In such eases I have not been able to convince 

 myself by any means which I could devise that the appearance 



