I 62 FERNANDUS PAYNE. 



sex differentiation has taken place in the same manner in all ani- 

 mals. In fact, the quotation from Morgan shows that two classes 

 of eggs are produced in phylloxerans and that the inequality of 

 the chromosome distribution is accomplished in some manner 

 at the time of the formation of the polar body. 



McClung, Stevens and Wilson in their studies on the chromo- 

 somes of the insects have argued that the accessory chromosome 

 and the idiochromosomes are either sex determinants or are in 

 some manner connected with the determination of sex. The 

 manner in which this is brought about yet remains a question. 

 Wilson ('06) gives two interpretations by which the end result 

 as we find it may be reached. First he follows out the earlier 

 hypothesis of Castle ('03) that sex production may be interpreted 

 as the result of a Mendelian segregation, transmission and domi- 

 nance of the sexual characters. This interpretation involves 

 two assumptions, neither of which have been proven, but which 

 he argues may not be insuperable difficulties. One is the assump- 

 tion that there are two kinds of eggs, the other, that selective 

 fertilization occurs. 



As an alternative point of view, he gives a second interpretation, 

 in which he suggests that possibly the differential chromosomes 

 may not be qualitatively different except in the degree of their 

 special activity ; or the end result may be due merely to a quanti- 

 tative difference in the chromatin. Wilson, himself, in his work 

 on Metapodius ('09), where the female may or may not have a 

 larger amount of chromatin than the male, has brought forward 

 evidence against the quantitative interpretation. 



My results in the present paper offer nothing new in regard 

 to the theory of sex determination, but are in perfect accord with 

 the majority of previous results on the insects. I shall not ven- 

 ture far into theoretical discussions. There is, however, one 

 question which naturally arises. Why do we have so few as one 

 and two chromosomes involved in the production of males and 

 females respectively in those forms with an odd chromosome, 

 and as many as five and eight in Gclastocoris? This is not so 

 strange, if the unequal distribution in these forms has arisen 

 from a pair of idiochromosomes as previously explained. In 

 every case whether the difference in number be one, two, three 



