THE MOSAIC STAGE OF DIFFERENTIATION 



269 



§ 13 



A word may be said as to certain problems of determination which 

 occur in later stages. As an example, we may take the case of the 

 spurs of fowls, grafted into hosts of the same or opposite sex, a few 

 days after hatching.^ As might be expected, grafts into hosts of the 

 same sex as the donor develop in the way characteristic for that sex, 



Fig. 126 



Differential behaviour of juvenile male and female spurs grafted into young 

 female fowls . The two legs of a hen 1 8 months old into which, when newly hatched, 

 two female spurs and one male spur had been grafted from day-old donors ;/. the 

 two grafted female spurs have remained the same size as the control spur (c.) 

 which has developed on the host; m. the grafted male spur has enlarged to the 

 dimensions characteristic of a spur on a normal cock. (Redrawn after photo in 

 Kozelka, jfoiirn. Exp. Zool. LXi, 1932.) 



remaining rudimentary in the female, but attaining a large size in 

 the male. Whereas, however, female spurs in a male host are 

 capable of male-type development (although, owing to an inhibi- 

 tory effect of male environment on female tissues, this is not 

 universal), male spurs on a female host regularly develop masculine 



^ Kozelka, 1932, 1933. 



