DEPARTMENT OF GENETICS. 119 



lation, but they may well have a considerable importance in exercising a 

 certain degree of control over the genetic constitution of the population of the 

 United States. The data thus collected make an extensive volume which is 

 being published in book form by the psychopathic laboratory of the municipal 

 court of Chicago. Though such novel and intimately personal legislation 

 has aroused very dijEferent opinions and emotions in people, the desirability of 

 a judicial review of legislation having such potentital eugenical bearing can 

 not be denied. 



THE PHYSIOLOGY OF REPRODUCTION AND DEVELOPMENT. 

 The Relation of Endocrines to Reproduction and Growth. 



Dr. Riddle has felt obliged to undertake this study because of difficulties 

 and exceptions encountered in his earlier (but still unpublished) work on sex, 

 and also because of its bearing on all genetic work on birds. It has received 

 much of his attention throughout the year. Miss Mary Holmes has given 

 valuable help with records, pedigrees, and computations concerned in these 

 studies. Summaries for parts of this work are still incomplete. The results 

 thus far obtained may be stated as follows: 



(1) Desiccated glandular products given by mouth are usually without 

 effect on birds; thymus, thyroid, and parathyroid are the chief exceptions. 

 The normal effects of most of these glands can be obtained only by injection 

 of extracts or suspensions. 



(2) Additional data suggest that the thymus gland of birds largely presides 

 over the secretion of egg-albumen and the egg-envelopes, and thus retains 

 the function which it probably had in the lower vertebrates. On this view 

 the thymus of mammals lost its function in the change to the mammalian 

 mode of reproduction. 



(3) McCarrison's conclusion is confirmed that the thymus persists throughout 

 life (perhaps it should be said during reproductive activity) in the pigeon, and 

 that the male thymus is nearly twice the size of the female thymus. Further, 

 in agreement both with this difference in size of thymus in the two sexes, and 

 with the current view that the thymus antagonistically affects the growth of 

 the gonads, it has been found that the testes of the male pigeon are retarded 

 in their growth for a longer (juvenile) period than is the (single) ovary of the 

 pigeon. 



(4) Moderate doses of thyroid substance are often capable of producing 

 reproductive abnormalities in healthy birds. Delayed and diminished egg 

 production and clutches of single eggs are among the observed irregularities. 

 Though there is reason to believe that such individuals exist, we have failed 

 thus far to find birds whose abnormalities of reproduction could be corrected 

 by the administration of thyroid. 



Other work of similar nature done by Dr. Riddle in cooperation during the 

 year is as follows : 



(5) The effects of repeated transplantation of suprarenals on young doves 

 (with Dr. Tadachika Minoura). The adrenals of the birds into which trans- 

 plants were repeatedly made did not measurably differ from the control, and 

 the time of sexual maturity was nearly the same in transplanted and control 

 groups. A notable amount of infertility and reproductive abnormality has 

 been obtained from the first-generation offspring of the transplanted birds. 

 The study of this point is being continued. 



