(1

Oct 9th 77 Primula sinensis

on Cot: placed transversely to light Cotyledon [sketch]

[data not transcribed]

(Used)

[345v]

17 17

Chap. 8

; and whilst eagerly The males wandering much about in search of the females and are thus they must often be exposed to greater various dangers. With many kinds of fish the males are much smaller than the females and are believed in some cases to be largely devoured by them latter & by other fishes. On the other hand with some birds the females appear to die in a larger numbers proportion than the males; and they are also liable to be destroyed on their nests, or whilst in charge of their young. With insects the larvæ of the females are often larger than those of the males, and would consequently be the most likely to be devoured. The females of some insects are, also, less active and less rapid in their movements than the males and would thus be less able to escape from danger. Hence with (animals 129 in a state of nature, in order to judgeing of the proportions of the sexes at maturity, we must rely on observations and mere estimation; which & this, except perhaps when the inequality is very great, are strongly marked, is but little trustworthy. Nevertheless as far as a judgement can be formed we may conclude from the facts given in the supplement, that the males of perhaps some few mammals, of many birds, of some fish and insects, appear considerably to exceed in number the females.

The proportion between the sexes fluctuates slightly during successive years: thus with race-horses

[Descent 1: 264-5: "They must, also, whilst wandering about in eager search for the females, be often exposed to various dangers. With many kinds of fish the males are much smaller than the females, and they are believed often to be devoured by the latter or by other fishes. With some birds the females appear to die in larger proportion than the males: they are also liable to be destroyed on their nests, or whilst in charge of their young. With insects the female larvæ are often larger than those of the males, and would consequently be more likely to be devoured: in some cases the mature females are less active and less rapid in their movements than the males, and would not be so well able to escape from danger. Hence, with animals in a state of nature, in order to judge of the proportions of the sexes at maturity, we must rely on mere estimation; and this, except perhaps when the inequality is strongly marked, is but little trustworthy. Nevertheless, as far as a judgment can be formed, we may conclude from the facts given in the supplement, that the males of some few mammals, of many birds, of some fish and insects, considerably exceed in number the females.
The proportion between the sexes fluctuates slightly during successive years: thus with race-horses, for every 100 females born, the males varied from 107·1 in one year to 92·6 in another year, and with greyhounds from 116·3 to 95·3."]

(2

Oct 10th Primula Sinensis

[data not transcribed]

(Used)

[346v]

16 16

Chap. 8

have been recorded during twenty-one years; and the male births have been to the females births as 99.7 to 100. with greyhounds the irregularity inequality is greater than with any other animal, for during twelve years out of 6878 births the male births have been as 110.1 to 100 female births. It is, however, in some degree doubtful whether it is safe to infer from the proportional numbers occurring under domestication, what which would occur be the cases under natural conditions; from those under domestication ; for slight and unknown differences in the conditions affect to a certain extent the proportions of the sexes. Thus with mankind, the male births in England are as 104.5, in Russia as 108.9, and with the Jews of Livornia as 120, to 100 females. The proportion is also mysteriously affected by the circumstance whether of the births being are legitimate or illegitimate.

For our present purpose we are concerned with the proportion of the sexes, not at birth, but at maturity, and this adds another element of doubt; for it is a well ascertained fact that with man, a considerably larger proportion of males than of females die die before or during birth, and during the first few years of infancy. So it almost certainly is with male lambs; & so it may be with the males or females of other may be with the lower animals. The males of some animals kill each other by fighting, or drive each other about until they become greatly emaciated;

[Descent 1: 263-4: "By indirect means, however, I have collected a considerable body of statistical data, from which it appears that with most of our domestic animals the sexes are nearly equal at birth. Thus with race-horses, 25,560 births have been recorded during twenty-one years, and the male births have been to the female births as 99.7 to 100. With greyhounds the inequality is greater than with any other animal, for during twelve years, out of 6878 births, the male births have been as 110·1 to 100 female births. It is, however, in some degree doubtful whether it is safe to infer that the same proportional numbers would hold good under natural conditions as under domestication; for slight and unknown differences in the conditions affect to a certain extent the proportion of the sexes. Thus with mankind, the male births in England are as 104·5, in Russia as 108·9, and with the Jews of Livornia as 120 to 100 females. The proportion is also mysteriously affected by the circumstance of the births being legitimate or illegitimate.
For our present purpose we are concerned with the proportion of the sexes, not at birth, but at maturity, and this adds another element of doubt; for it is a well ascertained fact that with man a considerably larger proportion of males than of females die before or during birth, and during the first few years of infancy. So it almost certainly is with male lambs, and so it may be with the males of other animals. The males of some animals kill each other by fighting; or they drive each other about until they become greatly emaciated."]