Watson, Weight of the Nervous System. 5 i 5 



still if we consider the weight of the mated females just at the 

 end of the period of gestation (before partuition), or better if we 

 add the weight of the young, immediately after birth to that 

 of the mother, we shall find that the weight of the breeding 

 female is in the ratio of 1. 164:1 to that of the male. The rela- 

 tionship after parturition (not adding the weight of the young 

 to that of the mother) is 0.848:1. 



Hensen in an Anhang to Edlefsen's work, made some 

 observations upon a litter of 4 guinea pigs, 3 females and i male, 

 in order to determine the relationships between the growth of 

 unmated females and males and thus supplement the results of 

 Edlefsen. To control his results he mated one of the females. 

 The following table presents his conclusions : 



Mated Unmated Unmated Male Ratio 



female female female 



I day after birth 59 gr. 63 gr. 57 gr. 59 gr. 1:1.03:0.96:1 



51 days after mating the 



one female 211 gr. 220 gr. 207 gr. 2j8 gr. 1:1.04:0.98:1.08 



117 days (immediately 



after parturition) 435 g'"- 468 gr. 407 gr. 582 gr. 1:1.08:0.94:1.34 



The weight of the mother just before parturition was 612 

 grammes. In this table we find some slight ground for infer- 

 ring that the males grow at least as rapidly as the unmated 

 females. On the other hand, the figures point to the fact that 

 breeding females, reckoning in the weight of their young, actu- 

 ally build up more bodily material, than either the unmated 

 females or males during a corresponding period of growth. 



Hensen then tried to determine the total increase in weight 

 of one mated female during the period of gestation, apart from 

 the increase in weight of her young. He began his reckoning 

 at the time pregnancy first became noticeable. This happened 

 on the 28th day after conception. The female weighed 335 

 gr. at this age. In the remaining 39 days of pregnancy (28 + 

 39 days = period of gestation) she herself gained lOO gr. in 

 weight and produced 146 gr. of bodily substances in young 

 and adnexa, i.e. 1.46 times more than she herself gained. 



MiNOT tabulated the average changes in the weights of 66 

 female guinea pigs, from the beginning of the period of gesta- 



