no C. M. CHILD. 



modified forms of mitosis as a possible basis for interpretation, 

 but the frequency and almost diagrammatic clearness of the cases 

 which I could interpret only as direct division, satisfied me that 

 no such interpretation was possible. I have pointed out (I., pp. 

 91-2) the difficulties attendant upon the observation of amitosis 

 in fixed material and the methods employed for giving the greatest 

 possible certainty. Cases of apparent division which appeared in 

 the slightest degree doubtful were not accepted as evidence. I 

 have demonstrated many cases of apparent amitosis to others, 

 both students and colleagues, who were able to see them with 

 perfect clearness and had no doubt of their being what they 

 seemed to be. 



On pp. 312-313 of his paper Richards says : " I must protest 

 against the balancing of results obtained from such unfavorable 

 material as that which cestodes offer against such favorable 

 objects for cytological study as for example the Orthoptera." 

 This protest involves somewhat peculiar ideas of cytological 

 study. Apparently, according to Richards, we must draw our 

 conclusions from " favorable" material and leave the unfavorable 

 aside. And apparently also because certain phenomena are 

 clearly visible in favorable material, e. g., the Orthoptera, we 

 must conclude that the phenomena in other less favorable mater- 

 ial are essentially similar. No field of biological science; and 

 perhaps no field of science in general, has suffered to such an 

 extent as has morphology from premature generalizations based 

 on observation of one or a few forms. Indeed it is perhaps not 

 too much to say that limited observation and premature attempts 

 at generalization often go hand in hand. 



As regards the " unfavorable " character of the Moniezia 

 tissues I must disagree to some extent with Richards. With 

 proper fixation, with sections sufficiently thin — most of mine 

 were 2-3 micra — and with careful staining and extraction, the 

 material is no more difficult to study, at least as regards nuclear 

 phenomena, than many other tissues. I have seen hundreds of 

 cases of apparent amitosis which were almost diagrammatic in 

 their clearness when observed with a little care, though of course 

 not as conspicuous as certain phenomena of mitosis in certain 

 species and cells. If observation of fixed and stained material is 



