138 Experimental Orchectointj hi Birds 



renewed growth of the testes after removal in this bird only led to the 

 reproduction of the original kind of gametes. 



Conclusions. 



Such arc the facts brought out by this investigation. Such as they 

 are, they seem to indicate that the cell divisions of the mother sperm- 

 cells which provide the new spermatozoa formed during regeneration 

 of the testis do not take place in exactly the same order, or are not 

 exactly of the same kind, as those which form the sperm-cells before 

 removal of the sex gland. 



Thus in Experiment 2 among the 17 young pigeons hatched after 

 castration of the male parent, four showed feathers on the tarsi and 

 toes, while among the 12 hatched before castration none were so 

 marked. 



Again in Experiment 3 (as has already been stated) the proportion 

 of Recessive Whites rose from 1 in 10 before, to 1 in 5 after castration 

 of the male parent. 



It is true that in Experiment 1 chickens hatched from eggs fertilijied 

 by Cockerel 7 when mated with three hens (sisters to cockerel) resemble 

 the chickens hatched from eggs by the same hens fertilized after the 

 testes had been regenerated. But the question of the genetic composi- 

 tion of this bird must be considered. If the bird was homozygous in 

 respect of this character of colour, that is to say if only one kind of 

 gametes were being produced before castration, then there is no reason 

 to think that the increased production of spermatozoa set going, during 

 regeneration of the testis after subcapsular orchectomy, would result in 

 the production of gametes of a different kind. 



The suggestion is, that in a sex gland where gametes of different 

 factorial composition are being produced the temporarily arrested and 

 the subsequently increased cell division due to the stimulus of removal 

 of the organ would be likely to result in a different rate, or order of 

 production of, the different kinds of gametes which are being formed 

 in that particular male organ. This can of course only be judged of by 

 a comparison of the zygotes which are hatched from eggs fertilized 

 by these male gametes before and after this stimulus of removal 

 has been applied. 



For this reason it seems desirable to simplify the conditions of the 

 experiment and to remove the male organs in fowls which are known 

 to be producing gametes of two kinds only. Further experiments 



