J. T. PATTERSON. 



deposited in the egg of the host. It was suggested that of the 

 nine complete, mixed broods listed, the origin of only five (broods 

 2, 3, 4, 6, 7, Table I.) could easily be explained in this obvious 

 way. In each of the four remaining broods (broods I, 5, 8, 9) 

 the great preponderance of females seemed to indicate that such 

 an explanation was not tenable. It was therefore suggested 

 that these mixed broods could have arisen from a single fertilized 

 egg, through a differential division of the two sex chromosomes 

 at one of the early divisions of the egg. In that connection the 

 following statement was made: "If Copidosoma conforms to the 

 general scheme for sex-determination in insects, the females 

 must have the 2 X chromosomes, and males the single X chro- 

 mosome. Ordinarily, during the process of cleavage, all of the 

 chromosomes in the fertilized egg divide equally, so that all of 

 the nuclei entering into the formation of the embryos will carry 

 the XX chromosomes, thus producing a brood of females. But 

 if during the early development of the egg it should happen that 

 the two X chromosomes in one or more cleavages should not 

 divide but separate, one going to each pole of the spindle, each 

 daughter nucleus would then receive a single X chromosome. 

 If such nuclei later divide in the typical manner and give rise 

 to embryos, such embryos would be males." 1 



Different workers have from time to time offered a similar 

 explanation to account for certain peculiarities in sex heredity, 

 and especially to account for the origin of hermaphrodites and 

 gynandromorphs. In doing so they have recognized the possi- 

 bility that a qualitative division of the hereditary material for 

 the sex factor may take place during cleavage. Their state- 

 ments refer of course to the development of a monembryonic 

 egg, in which the products of any somatic segregation must 

 necessarily be distributed to different parts of the same embryo. 

 In the case of a polyembryonic egg, a similar segregation, if 

 occurring early enough in cleavage, would result in the pro- 

 duction of two groups of embryos of different sexuality, and upon 

 completing their development these two groups of embryos 

 would produce a mixed brood. 



It was this kind of evidence, although meager in amount, 



1 Loc. cit., p. 356. 



