3O2 J. T. PATTERSON. 



hatched. All but twenty-two of these larvae were fixed at vari- 

 ous stages of development, in order to secure material for the 

 study of the unfertilized parasitic egg. Three of the twenty- 

 two caterpillars eventually reach full or nearly full growth. 

 Two of these showed signs of disease, and were killed, the para- 

 sitic larvae being removed and fixed for cytological study. A 

 study of sections of the larvae from both caterpillars fail to show 

 anything but male larvae present. The third caterpillar formed 

 a carcass, from which 1,842 males emerged. To this must be 

 added 100 more individuals, which were removed from the 

 carcass in the pupa stage and fixed for cytological purposes. 

 The sections show that all the pupa are males. These results 

 indicate that the unfertilized egg of Paracopidosomopsis produces 

 males only. 



A study of the spermatogenesis as revealed in these pupae 

 shows that males developed by parthenogenesis carry the haploid 

 number of chromosomes, while a study of maturation of the 

 eggs and fertilization shows that females, as would be expected, 

 carry the diploid number. With these facts established, it will 

 be possible to determine whether two types of males are pro- 

 duced, as may be shown by the following consideration. If 

 Paracopidosomopsis conforms to the general scheme of sex deter- 

 mination in insects, the chromosomal formula for the fertilized 

 egg may be represented by N + 2X, in which N represents the 

 non-sex chromosomes, and that for the unfertilized egg by 



N 



-f- X. Now, should males also arise from the fertilized egg, 



their formula must be N -f- X. The presence of the double 

 number of non-sex chromosomes in such individuals should not 

 affect their sexuality, because in all forms in which partheno- 

 genesis is absent, males are represented by this or a slightly 

 modified formula. Modern genetic studies have shown that 

 maleness or femaleness is determined by the number of X 

 chromosomes present in the egg, and not by the number of non- 

 sex chromosomes. Even in forms which have the Y chromosome, 

 the presence or absence of the Y does not seem to affect the sex 

 of the individuals. 



