118 CARNEGIE INSTITUTION OF WASHINGTON. 



modification of the number of eggs ovulated in any oestrus cycle. One 

 of these concerned the influence of removal of one ovary on the number of 

 eggs subsequently ovulated. The left ovary was removed by Dr. 

 MacDowell from 50 adult female mice; subsequently the animals were mated 

 and counts made of the corpora lutea. The question has been investigated 

 before, and it had been found that the single ovary compensates for the loss of 

 its mate. In our experiments the number of corpora lutea in the remaining 

 ovary average about 1 greater than the average produced by two ovaries in 

 our normal females. Thus the single ovary fully compensates and, perhaps, 

 even overcompensates. However, the number of young born from semi- 

 spayed mothers (4.6 per litter) was less than from normal females of the same 

 strain (5.6 per litter). This reduction in the number of young which come 

 to birth is probably an adjustment to the limitations of space in the single 

 horn of the uterus in which all of the young must develop, since passage of 

 embryos to the opposite horn is mechanically almost impossible. 



Blood-Sugar Values in Generic Crosses. 



As was stated in our report for the last year (Year Book for 1922), Doctors 

 Oscar Riddle and H. E. Honeywell have cooperated in studying the inheri- 

 tance of blood-sugar values in hybrids between the Japanese turtle-dove 

 (Turtur orientalis), which has on the average about 188 mgm. of sugar per 

 100 c.c. of blood, and the ring-dove (Streptopelia alba), which has an average of 

 149 mgm. of sugar per 100 c.c. of blood. The Fi hybrids have an intermediate 

 amount of blood sugar. This year further progress has been made on this 

 topic. Fi hybrids have been obtained between a Spelopelia and Streptopelia, 

 and these, likewise, show a blood-sugar value that is intermediate between 

 those of the parent genera. 



The Fi hybrids of TurturX Streptopelia have been back-crossed to Strepto- 

 pelia, and the hybrids of this generation give an average blood-sugar value 

 that is intermediate between that of the Fi and Streptopelia. The blood- 

 sugar value is apparently inherited in the same way as body-size. It is a 

 complex of several factors, and, it may be predicted, will follow the rules of 

 multiple-factor inheritance. Dr. Riddle points out that the new sugar 

 values found in the hybrids are maintained throughout life, and that such a 

 different value requires new adjustments of equilibrium on the part of all 

 tissue components throughout the developmental period of the hybrid; also, 

 that these adjustments supply one possible basis for various irregularities 

 in the behavior of characters in hybrids derived from wide crosses. 



Relation of Reproductive Overwork to Carbohydrate Metabolism. 

 Last year this Department reported new light upon the mechanism of 

 "reproductive overwork" through the discovery that the suprarenal glands 

 of female pigeons undergo marked and prolonged hypertrophy in very exact 

 coincidence with each ovulation period, and by the further observation that 

 the carbohydrate metabolism of the bird undergoes a simultaneous change, 

 as shown by an increased concentration of the sugar of the blood. These 

 results have been extended, confirmed, and published by Dr. Riddle. The 

 conclusions drawn from the studies on suprarenal hypertrophy are as follows : 



"In four kinds of healthy doves and pigeons the weight of the suprarenal 

 glands has been found to increase at each ovulation cycle and the point of 



