210 HEREDITARY CHARACTERS 



regard to sex ; that all the males were pure recessives 

 (homozygous) and carried only the male character; and 

 that the grossulariata character could not be borne by a 

 female bearing gamete. The Mendelian interpretation of 

 the transmission of sex has already been dealt with, 1 but 

 the behaviour of the lacticolor character seems readily 

 explicable as a secondary sexual character. This might 

 appear to be a somewhat wild guess, were it not that 

 another variety of Abraxas grossulariata is known to be 

 sexually dimorphic. 2 In the variety varleyata, the male 

 has white rays upon its wings. These rays are generally 

 present on the hind-wings only, and are usually from two 

 to five in number. 3 They are very noticeable and produce 

 a very pretty effect. They are apparently never present in 

 the female. 



The conclusions arrived at may be briefly summed up as 

 follows : As bi-parental reproduction tends to eliminate all 

 useless variations this effect must be accentuated when the 

 sexes are separate, that is, when any given individual pro- 

 duces only sperms or only ova, for inbreeding cannot then be 

 so close as when every individual produces both sperms and 

 ova. Sex being therefore advantageous to the race, has 

 been produced by the action of natural selection upon 

 individual variations. As the utility of sex depends upon 

 the two characters remaining separate, the effect of natural 

 selection has, while preserving and accentuating them, pre- 

 vented their tendency to blend, as racial characters generally 

 do. That variations towards blending do occur is shown by 

 the occurrence of hermaphrodites in species where the sexes 

 are generally separate. The fact that sex is transmitted in 

 an alternative manner like individual characters, has led 

 some observers to consider sex as an ordinary individual 

 or Mendelian character. The fact that the secondary sexual 



1 See pp. 197, 202. 



2 Porritt, G. T., Entomologist's Montldy Magazine, Second Series, vol. xviii. 

 p. 12, 1907. 



3 Mr. Porritt describes one example which has "six rays on each fore-wing 

 .and seven and six respectively on the hind- wings," op. cit. 



