C. J. Bond 139 



should also be undertaken showing the effect of partial removal of 

 the ovary in heterozygous hens, in order that the influence of re- 

 generation may be tested in the case of female as well as male 

 gamete-forming organs. There is, I think, no doubt from experimental 

 evidence that the ovary in the Fowl does undergo regeneration after 

 partial destruction or removal. 



Thus the ovary was destroyed by the actual cautery in a hen 

 aged 1 year as far as could be seen with the naked eye wholly. On 

 examination 1 year and 9 months after the operation the ovary was 

 found to be fully regenerated and functionally active, a number of eggs 

 having been laid, see PI. V, fig. 10. 



If these results are confirmed, that is to say, if it can be shown that 

 the effect of the stimulus to renewed growth which follows castration, 

 is to alter the character of or the proportionate rate of cell division in, 

 the cells which produce the male gametes then it will be necessary 

 to study these changes in cell division in detail, because it is possible 

 that certain results in breeding which seem to be inconsistent with 

 Mendelian expectation may owe their apparent anomaly to some change 

 in the rate of reproduction of gametes of different kinds in that particular 

 sex gland. 



For instance, the normal relative proportion of male to female 

 chickens hatched at different times of the year varies, and this fact 

 suggests a seasonal difference in the relative production of male and 

 female zygote-forming sperm-cells. 



[The explanation of Plates IV and V is to be found on the plates 

 themselves.] 



