GONADS AS CONTROLLERS OF CHARACTERISTICS 



461 



with the bread and milk and a small amount of grain (corn or 

 oats) placed in the cage once each week. The rats were allowed 

 to eat all they would at one time each day and weighings were 

 made seven to ten hours after the meal. 



Gonadectomy was performed under anesthesia at ages of 

 twenty-three to thirty days, and the gonads were removed from 

 both sexes by a midventral incision. 



Table 1 is a tabulation of the material used; the normal male 

 and female served as controls, though the relation of operated to 

 unoperated animals is not considered in this paper. 



TABLE 1 



Stotsenburg has already stated that, at about 200 days old, 

 many times rats are affected by certain ailments that interrupt 

 the ascent of the normal growth curve, and for this reason, as 

 well as on account of the death of several animals, the weight 

 records only include growth up to 180 days. But considerably 

 before this time the rats would have been sexually mature and 

 entirely adult. 



Table 2 is a tabulated record of the average weight of indi- 

 viduals of each sex in each litter from the time of operation up 

 to the 180th day, as well as the number of individuals of each 

 sex in the litter at that age; the last column is the percentage of 

 the weight of the males above that of the females at each weigh- 

 ing, the percentages having been calculated from the average 

 weight of the individuals of each sex as given in the table. An 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 28, NO. 3 



