146 CARNEGIE INSTITUTION OF WASHINGTON. 



tion to narmal fuactioning of most of these birds which produce egg 

 abnormalities and embryos characterized by early deaths. Further 

 investigation of this general problem is in progress. 



A comprehensive study of the possible relation of nutritional 

 deficiency to the above-mentioned reproductive abnormalities and 

 embryonic deaths has been nearly completed during the year. The 

 results lead to two conclusions of importance: (a) Few, if any, of the 

 reproductive abnormalities and embryonic deaths referred to above 

 are caused by insufficiency of vitamines A, B, or C; nor are they 

 caused by lack of Ca, K, P, Na, CI, S, Fe, Mn, As, or Si; nor by a de- 

 ficiency of a long series of amino acids. These results, together with 

 additional negative tests made with other glandular tissue and the 

 positive results obtained with thymus and parathyroids, permit the 

 conclusion concerning the specific deficiency of the two last-named 

 organs. (6) This practical demonstration of the freedom of our 

 present material from nutritional deficiency, at the only time such 

 deficiency has been suspected, affords ample and most desirable evi- 

 dence that in our earlier prolonged quantitative study of one or another 

 aspect of the metabolism of these doves there has been little or no 

 complication of the results traceable to nutritional deficiency. 



Transplantation of xVdrenai.s and Gonads into Dovrs. 



Dr. Riddle is making, in collaboration with Dr. Tadachika Minoura, 

 a guest of the Department, a study of the possibilities and effects of 

 repeated adrenal transplantation upon young and maturing ring- 

 doves. Certain associations of the adrenals and the gonads make it 

 desirable to learn as much as possible of the special relations which 

 may exist between these as well as other endocrine glands on the one 

 hand and the various aspects of sex-development and of reproduction 

 on the other. 



Dr. Minoura has utilized a specially suitable part of our material 

 during much of the past year for the transplantation of testis or ovary 

 upon the growing embryo or upon the very young dove. It has been 

 found advisable to rear most of these operated embryos and young to 

 or beyond the period of maturity. 



In addition to the studies noted above. Dr. Minoura is utilizing a 

 group of birds in our collection, and a part of the weight records earlier 

 obtained by Dr. Riddle, for the construction of the normal growth- 

 curve of the ring-dove. In this connection he is particularly seeking to 

 identify the exact time of the rather sudden enlargement of the gonads 

 (which occurs at maturity in the dove) with a definite and unusual 

 feature of the dove's growth-curve. 



The Origin and Interpkkt^tion of One-Yolk Twins in Doves. 



Dr. Riddle has long been looking for one-yolk twins in pigeons, 

 since the material is highly advantageous for the study of this phenom- 



