298 J. T. PATTERSON. 



examination of these parasitized eggs in carefully teased prepara- 

 tions showed that the parasite had laid two eggs in eleven cases, 

 and a single egg in six cases. The same experiment performed 

 with fertilized females shows the same result. In a total of 

 forty-two ovipositions made by three unfertilized and sixteen 

 fertilized females, two eggs were laid in twenty-eight cases and 

 one egg in fourteen cases. 



While these observations show conclusively that two eggs are 

 frequently deposited simultaneously by the insect, yet they do 

 not settle the question as to whether the fertilized female can 

 lay both kinds of eggs. However, a study of smear prepara- 

 tions and sections shows that in many cases both eggs are 

 fertilized. For this, as well as for other reasons, the writer is 

 of the opinion that any suggested explanation involving the 

 idea that an unfertilized and a fertilized egg is laid in the egg of 

 the host is inadequate to account for all of the mixed broods in 

 Paracopidosomopsis. 



This brings us to a consideration of the second suggestion, 

 namely, that a fertilized egg may give rise to males and females. 

 This result could be attained by the abnormal behavior of the 

 sex chromosomes in one or more of the cleavage divisions. There 

 are several different ways in which an abnormal behavior of the 

 sex chromosomes might occur. Some of these possibilities are 

 too improbable to receive consideration, but there are three or 

 four that we shall mention. First, by somatic disjunction, 1 by 

 which is meant the separation instead of division of the two sex 

 chromosomes in a cleavage mitosis. Second, by somatic non- 

 disjunction, by which is meant the failure of the two daughter 

 chromosomes of one of the X's to separate after the division of 

 both sex chromosomes had occurred. This would result in one 

 daughter cell receiving three sex chromosomes, the other a 

 single X chromosome. A third possibility is that only one 

 X chromosome might divide, resulting in the formation of one 

 cell with two X's and another with only one X. Finally, we may 

 mention a fourth possibility, namely, that a division might occur 

 in which all the sex chromosomes, whether divided or not, pass 



1 This term is not entirely exact, because of the implication that the separating 

 chromosomes had previously been united, which of course is not the case. 



