288 THE DESCENT OF MATT. 



species in the latter genus, 63 specimens canglit the same day included 

 57 males; but lie suggests that this preponderance may'be clue to 

 some unknown difference in the habits of the two sexes. With one 

 of the higher Brazilian crabs, namely, a Gelasimus, Fritz Miiller 

 found the males to be more numerous than the females. According 

 to the large experience of Mr. C. Spence Bate, the reverse seems to 

 be the case with six common British crabs, the names of which lie 

 has given me. 



Tlie Proportion of the Sexes in Relation to Natural 

 Selection. There is reason to suspect that in some cases 

 man has by selection indirectly influenced his own sex- 

 producing powers. Certain women tend to produce during 

 their whole lives more children of one sex than of the 

 other; and the same holds good of many animals, for 

 instance, cows and horses; thus Mr. AVright, of Yeldersley 

 House, informs me that one of his Arab mares, though put 

 seven times to different horses, produced seven fillies. 

 Though I have very little evidence on this head, analogy 

 would lead to the belief that the tendency to produce 

 either sex would be inherited like almost every othei 

 peculiarity, for instance, that of producing twins; and con- 

 cerning the above tendency a good authority, Mr. J. 

 Downing, has communicated to me facts which seem to 

 prove that this does occur in certain families of short-horn 

 cattle. Col. Marshall* has recently found on careful 

 examination that the Todas, a hill tribe of India, consist 

 of 112 males and 84 females of all ages that is in a ratio 

 of 133.3 males to 100 females. The Todas, who are poly- 

 androus in their marriages, during former times invariably 

 practiced female infanticide; but this practice has now 

 been discontinued for a considerable period. Of the chil- 

 dren born within late years the males are more numerous 

 than the females in the proportion of 124 to 100. Col. 

 Marshall accounts for this fact in the following ingenious 

 manner: " Let us for the purpose of illustration take three 

 families as representing an average of the entire tribe; say 

 that one mother gives birth to six daughters and no sons; 

 a second mother has six sons only, while the third mother 

 has three sons and three daughters. The first mother, fol- 

 lowing the trioal custom, destroys four daughters and pre- 

 serves two. The second retains her six sons. The third 

 kills two daughters and keeps one, us also her three sons. 



*"The Todas," 1873, pp. 100, 111, 1&4, 196. 



