1909.] 



Gametogenesis of the Gall-Fly, etc. 



105 



producing (arrhenotokous) female. In the Bee, as far as is known, all queens 

 produce similar eggs, and this would be accounted for by the degeneration of 

 one kind of spermatozoa. 



The sex-determination in the Gall-fly would then take place as follows : — 

 The spermatocytes of the male would bear a determinant for nialeness, 

 which may be represented by the symbol J*. At the nuclear division this 

 passes into one daughter-cell, its fellow being without it and thus containing 

 no sex-determinant, a condition which may be represented by the symbol 0. 

 The fertilisable eggs after maturation are supposed all to bear one determinant 

 for femaleness, represented by the symbol ? . The zygotes all develop into 

 parthenogenetic females, but since half of them were fertilised by -bearing 

 spermatozoa, and half by spermatozoa with no sex-determinant (0), the 

 former will have the constitution ? J" , the latter ? 0. The females with 

 constitution ? (J lay eggs which undergo maturation ; the ? determinant is 

 expelled, and the egg left with the J" determinant becomes a male. The 

 females with constitution ? 0 lay eggs which undergo no reduction, but 

 containing the ? determinant develop into females. The ? determinant is 

 transmitted to the eggs of the summer generation, and since only one sex- 

 determinant is present in the egg, it remains in the pronucleus when the 

 polar mitoses take place, with the result that all eggs of the summer generation 

 are ? -bearing, as is assumed above. 



It now remains to be seen whether this scheme is consistent with what 

 is known of sex-determination, first in ordinary cases where all eggs are 

 fertilised and secondly in the Bee and other aculeate Hymenoptera. The 

 ordinary bisexual cases will be considered first. 



As the result of my work on heredity and sex-determination in the moth. 



Abraxas grossulariata* and of other similar cases, Batesonf suggested the 



hypothesis that the female is heterozygous in respect of sex, containing male 



and female determinants, the male homozygous containing only male. Eggs 



w^ould thus be produced in equal numbers bearing maleness or femaleness, but 



all spermatozoa would bear the male determinant. This hypothesis would 



completely explain the cases which led to its formulation, but it is not 



completely consistent with the existence in many insects of two kinds of 



spermatozoa, one containing a heterochromosome and one without it. More 



recently, the evidence from some forms of sex-limited inheritance, such as 



colour-blindnessj and congenital nystagmus,§ have made it clear that there 



* ' Evol. Committee Eoy. Soc, Keport IV,' 1908. p. 53. 

 t ' Science,' 1908, N.S., vol. 27, p. 785. 



I Bateson, " Mendel's Principles of Heredity," ' Camb. Univ. Press,' 1909, 

 1st impression, p. 230, inserted slip ; 2nd impression, 1909, p. 195, note. 

 § See Lloyd Owen, ' Ophthalmic Eeview," vol. 1, 1882, p. 239. 



