A, PEZARD 281 



It would be interesting to determine the variation with age of the 

 total decline, the constant of regression C, and also the time 6. It is 

 possible that C diminishes with age, while 6 increases. But the num- 

 ber of experiments at our disposal do not permit us to affirm it. At 

 all events, by the same method of reasoning, we may regard as 

 established from now on the fact that C and 6 are bound to each other 

 by a simple relation. To demonstrate this point, we shall base our 

 reasoning on the figures derived from our experiments on castration 

 followed by transplantation. 



Intrapuheral Castration. 



The following observations have no bearing on the cocks which had 

 acquired or nearly acquired their secondary sex characters, but upon 

 those birds which were castrated at the time when the development 

 of these characters was beginning (intrapuberal castration). As the 

 diminution in the comb is then slight, one might expect to find a 

 slow regression similar to that which characterized the end of the 

 regression period in the previously observed birds the experiment 

 confirms this hypothesis. 



Experiment 7. — Cock, mixed breed, hatched at the Physiological Station in 

 Aug., 1911. Castrated Jan. 22, 1912. Received testicular transplantations at the 

 time of castration. For 3 weeks the comb regressed; then its development recom- 

 menced under the influence of the transplantations. The regression and even the 

 resumption of development have a clearly parabolic curve (Fig. 9). 



We had calculated C, 0, and / starting from the formula 



obtaining successively 



whence 



Experiment 8. — Cock, same conditions of experiment and same succession of 

 observations as in the preceding case (Fig. 9). The calculations are the same as 

 in Experiment 7, according to the general formula 



