NEWLY MATURE FEMALES 411 



ovulation and in this class the mean number of ovulations preceding conception was 1-42. Owing to 

 the small size of the sample the variance is quite large. It is of interest that in primiparous females 

 any corpora albicantia will represent unsuccessful ovulations. 



MONTHS 



Text-fig. 36. Monthly mean foetal lengths for all pregnant females (solid line) and 

 for primiparous females (dotted line). 



0,1,2, C. A. 



J F 



M J J A 



MONTHS 



Text-fig. 37. Monthly frequencies of conception for different classes of pregnant females. P, , first pregnancy diagnosed 

 from mammary glands; o, 1, 2 and 0-1, number of corpora albicantia. The mean conception dates ± 2 S.E. are indicated. 



There are conspicuous differences in the timing of the pregnancy of primiparous females compared 

 with multiparous females. In Text-fig. 36 the mean monthly foetal lengths for all pregnant females 

 and for females known to be primiparous, from examination of the mammary glands, are set out for 

 comparison. The rates of growth of both groups of foetuses appear to be similar, but the first-pregnancy 

 'oetuses seem to be retarded by about a month compared with those of multiparous females. 



