36 THE EVOLUTION OF SEX. 



Heycx : —In Leontarus domestica, according to Rumpf, the female plant 

 may bear male blossoms l:»efore its proper female flowers. In Morns nigra^ 

 and in other cases, according to Miller, male flowers may be borne first, 

 and afterwards fruit. Treviranus observed that the first flowers of beech, 

 chestnut, and other trees are male. Clausen gives similar examples ; and 

 Hoftmann notes that in the horse-chestnut, and several other cases, male 

 flowers appear first, and afterwards hermaphrodites or females. 



Most of the results in regard to the influence of age are, 

 however, extremely unsatisfactory and conflicting. This is 

 evident from the above statistics. The law of Hofacker and 

 Sadler cannot be regarded as in any sense established. In 

 fact, as Hensen remarks, unless statistics are enormously large 

 they prove very little. 7^he number of other factors besides 

 parental age which may operate in any case is evidently great, 

 — health, nutrition, frequency of sexual intercourse, abstinence 

 after the birth of a male, and the like, all reduce the feasibility 

 of the statistical method. At present, at any rate, we are not 

 justified in ascribing much importance to the relative age of the 

 parent except as a secondary factor, influential doubtless in 

 relation to nutrition. 



§ 7. Comparative Vigour. — The best known, and probably 

 still most influential, theory is that of " comparative vigour." 

 As elaborated by Girou and others, this hypothesis connects 

 the sex of the offspring with that of the more vigorous parent. 

 It cannot be said, however, that facts bear out the case. Thus 

 consumptive mothers produce a great excess of daughters, 

 w^hile Girou's theory would lead us to expect the opposite. 

 We require in fact to have " vigour " analysed out into its 

 component factors, and in so doing we shall afterwards find 

 not only facts but reasons in favour of the conclusion, in part 

 included in the above theory, that highly nourished females 

 tend to produce female offspring. That form of the hypothesis 

 which refers the determination of sex to " genital superiority," 

 or to " relative ardency," can hardly be seriously considered. 

 In this connection it has been maintained that in " marriages of 

 love," after a short betrothal, female offspring predominate ; 

 and a number of other interesting facts of a like nature are 

 suggested. Some scepticism as to the practicabihty of such 

 inductions is, however, inevitable. 



v^ 8. Starkiveather' s Law of Sex. — Closely allied to the 

 theory of comparative vigour is that elaborately worked out by 

 Starkweather, which is suggestive enough to deserve separate 

 summary. He starts from a discussion of the alleged superiority 



