408 L. DONCASTBR 



somes and the dlimiiiaiiou plntf; in any given section corre- 

 spond very closely in their staining properties, although in 

 ditferent sections very different results were obtained from the 

 same combination of stains. 



V. Jjorax Carmine and Picro-indigo-carmine. 



Sections were stained in borax carmine for forty-eight 

 hours, followed by picro-indigo-carmine for ten minutes. 



The chromosomes were found to be dark red, and the 

 elimination plate and spindle-hbres yellowish. Although this 

 method did not appear to give support to the view that 

 chromatin is present in the elimination plate, it does not 

 disprove that hypothesis, for in some sections even the chromo- 

 somes themselves were barely stained with the carmine, so 

 that it is not surprising to find the elimination plate unstained 

 even though it may contain chromatin, for this eliminated 

 chromatin would almost certainly be undergoing disintegration. 

 In sections stained by other methods as given above, it was 

 not unusual to find that the elimination plate was unstained, 

 even though it had previously stained deeply with iron haema- 

 toxylin. 



These staining experiments, although not conclusive, give 

 a considerable weight of evidence in support of the hypothesis 

 that there is a certain amount of chromatin left behind, on 

 the equator of the spindle, by the chromosomes when they 

 move apart at anaphase. If this be true ' it is at least conceiv- 

 able that the sex-chromosome, in the eggs of all-female broods, 

 eliminates so much that it becomes functionless as regards 

 sex-determination V ^i^d that here may lie the explanation of 

 the production of all-female families from eggs some of wliich 

 contain twenty-seven and others twenty-eight chromosomes. 



From conversation with Professor Doncaster, as well as from 

 his own argument in this paper, I know that this was the 

 conclusion at which he himself had arrived. 



E. C. B. 



' p. 406. 



