468 L. V. DOMM AND MARY JUHN. 



The latent period is much shorter when adult birds are uni- 

 laterally castrated and here the right isolated testis hyper- 

 trophies at the same rate and in the single case available even to 

 a slightly greater degree than the left (Table IV.). 



Comparison with the averages of the controls rather than with 

 single controls as set forth in the tables increases the probability 

 of these conclusions as examination of Table V. shows. Indi- 

 vidual cases emphasize these general conclusions (Table I., Nos. 

 53, 44, 46. Table II., Nos. 815, 824, 845. Table IV., Nos. 

 114, 121). 



Lipschiitz's suggestion for mammals that unilateral castration 

 produces only a more rapid rate of growth rather than a definitive 

 compensatory enlargement of the surviving gonad does not seem 

 a probable interpretation of our results. It would mean that 

 there would be no actual plus in weight of the isolated gonad 

 over one of the control testes pair at the end of the develop- 

 mental period of the glands. Such a statement requires a 

 definition of the endpoint of growth of the testes, and in view of 

 the normal variation in the weight of the testes as well as the 

 seasonal variation the feasibility of such an absolute determina- 

 tion appears questionable. 



The cocks are mature at thirty-two weeks and compensatory 

 hypertrophy as defined is demonstrated not only at this time but 

 as late as forty-eight weeks. 



III. NORMAL SIZE RELATIONS OF RIGHT AND LEFT TESTES. 



During the course of the experiments we accumulated some 

 data on the size of the right and the left testes of normal cocks. 

 The majority of the observations were made on the gonads of 

 different birds but the records of the control birds in the pre- 

 ceding tables are for pairs. Tables VI. and VII. give the 

 measurements obtained in one week old chicks. The length 

 and width of the right and left testes are given as it was im- 

 practicable to secure accurate weights. The weights of the 

 chicks are also stated for comparison. There appears to be a 

 very slight advantage in size on the part of the left testes at 

 this age. In older birds we find such an individual variation 

 occurring in birds of the same age and even of approximately 



