A. PfZARD 



275 



llOt 



3 4 5 6 7 8 9 10 11 12 

 Time in weeks 



Fig. 3. 



Experiment 3. — Cock, Black Orpington, about 8 months old. Castrated Dec. 

 4, 1909. The bird, whose sexual growth was slow, did not yet possess its sec- 

 ondary sex characters. It received from Jan. 17 to May 23, 1910, frequently 

 repeated injections of testicular extract of the undescended testicle of a pig. 

 Under this influence the comb developed and reached its normal length (86 mm.). 



