Il6 CM. CHILD. 



I am inclined to believe that the relative frequency of mitosis and 

 amitosis in certain species, and even in single individuals, e. g., 

 Planaria may vary greatly according to conditions, it is also 

 possible that Richards' material differs more or less widely from 

 mine. 



And now a few words concerning Richards' attempts at inter- 

 pretation of my observations on the germ cells. On p. 315 he 

 suggests that I have been misled by mistaking for a nucleus or 

 part of a nucleus a mass of " Nebendotter " which occurs in 

 " some of the early oogonia . . . while it is not present in some 

 oocytes" (p. 313). That one investigator working with one 

 species should be willing, without more positive evidence than 

 Richards has anywhere brought forward, to attribute to another, 

 of wider experience than himself, and working with a different 

 species and genus, so gross an error of observation as this is, to 

 say the least, somewhat surprising. But the facts are these : as 

 I have noted above, amitosis occurs in the earlier stages of de- 

 .velopment of the ovary and in such stages the primitive germ 

 cells certainly contain no " Nebendotter." As a matter of fact, 

 I have never seen anything of the sort at any stage in the ova of 

 Moniezia, although the cells of the vitellaria, which in certain 

 stages may easily be mistaken for ova, develop such masses 

 rather early in their history, but usually not until division has 

 ceased (see Child, I., Figs. 31-35, and pp. 11 2-3). I cannot 

 see that my accounts of nuclear structure and division afford any 

 possible basis for the relief that I could have mistaken for a 

 nucleus a body which according to Richards stains readily with 

 iron haematoxylin and appears " as a dark homogeneous mass 

 even after a great deal of extraction," by which "nucleus and 

 cytoplasm may be entirely decolorized " (Richards, p. 314). More- 

 over I have employed various methods of staining which leave 

 the yolk almost wholly unstained. 



Concerning the slight difference in color between the two parts 

 of a nucleus, which I noted occasionally (Child, I., p. 95), it 

 need only be said that I have often observed such differences in 

 the somatic cells of Moniezia^ as well as in the somatic cells of 

 other forms, where there can be no question concerning 

 " Nebendotter," consequently Richards' suggestion (p. 315) that 



