4 20 DISCOVERY REPORTS 



mature females which have ovulated only once (A) or twice (B). These data are presented in Table 15, 

 groups B + C and group E respectively. The probable range of error of the estimated mean growth 

 curve for females which attain puberty in the breeding season at a mean length of 65-25 ft. (from 

 Text-fig. 39) is also shown by the dotted lines. The mean date of sampling is mid-February. 



When the mean length of the once-ovulated group is compared with that of the twice-ovulated 

 group there is seen to be a difference of 1-3 ft. The standard error of the difference between these two 

 means is 0-554, which means that the difference is statistically significant. If the twice-ovulated group 



MAMJJASONDJ FMAMJJASON DJ FMAMJ 



MONTHS 



r 



PAIRING 



i 



r 



PAIRING 



1 



Text-fig. 41. Growth of newly mature females. The mean lengths ±<r and 2 s.E. of nulliparous or primiparous females which 

 had ovulated twice (Bj, B 2 ) are duplicated one year apart for comparison with the growth curve of once-ovulated, nulliparous 

 or primiparous females (A). See text for explanation. 



attained puberty and ovulated at about the same time as the once-ovulated group it is very unlikely 

 that there would be such a discrepancy between the mean lengths of the two samples. The mean 

 values for the once-ovulated females which were primiparous or nulliparous (Text-fig. 39 B and C) 

 are in very close agreement with each other. 



If the twice-ovulated group is plotted a year later (B 2 ) its mean length (68-2 ft.) is seen to be close 

 to the length (68-5 ft.) of the group of females known to be in their first lactation or resting period 

 (Table 15). That is to say, pregnant females in the '1 corpus albicans' group probably become 

 pregnant about a year later than the 'o corpus albicans' group. The mean length of the twice- 

 ovulated group under consideration coincides with the estimated lower limit of the growth curve of 

 the 'o corpus albicans' group of pregnant females (Text-fig. 41, curve a---a) which on average attain 

 puberty and pair in July. The estimated time of pairing of the ' 1 corpus albicans ' group is also July 

 (Text-fig. 37), when this lower curve (a---a) has attained a length of nearly 68 ft., which is nearly 3 ft. 

 more than the mean length at puberty. It will be remembered that the growth in length in the first 

 year after puberty was taken to be just over 3 ft. The origin of this curve (a---a) at the mean length at 

 puberty is in October, some months after the peak pairing season, but having regard to the length 

 variance of the group concerned they could well have attained puberty as late as December or January. 



