E. A. COCKAYNK 127 



Conclusions. 



1. Gynandromorphs probably fall into three groups. The first two 

 groups contain a majority of symmetrical gynandromorphs showing a 

 blending or fine mosaic of male and female characters, and some showing 

 characters predominantly male or female, but having on the wing 

 streaks with the colour and pattern of the opposite sex. 



These are unisexual or have se.x glands containing mingled ovarian 

 and testicular tissue. 



The third group contains the completely and almost completely 

 halved gynandromorphs, some with a coarse mosaic arrangement and 

 some with a fine mosaic arrangement of sexual characters. 



2. The first group is due to a difference in the potency of the 

 factors for sex, or secondary sex characters, or both, occurring in the 

 two parents. The characters behave as simple Mendelian dominants 

 and recessives, respectively. This difference occurs in Lymantria di-spar, 

 and its var. japonica. 



3. The second grouj) is probably due to a failure in the noruial 

 process of fusion of the sex chromosomes of the spermatozoon- and ovum. 

 This is especiall}' liable to occur in the cases where the parents are of 

 diff"erent species. 



4. In the third group the condition is due to an irregular distribu- 

 tion of the chromatin, which carries the factors for sex and for secondary 

 sexual characters or for one of these alone, to the first two cleavage 

 cells. Thus it occurs at a late stage in mitosis and not at an early 

 stage as in the first two gi'oups, and the first two cleavage cells are 

 different instead of being alike in their chromatin. 



5. A similar irregular distribution of the chromatin carrying a 

 somatic character may take place, and this leads to heterochroism. 



6. An irregular distribution of both sex and somatic factors may 

 occur together and this leads to the production of a heterochroic 

 gynandromorph. 



7. The existence of these strictly parallel groups of heterochroic 

 insects, simple gynandromorphs, and heterochroic gynandromorphs 

 supports the view that sex is a Mendelian unit character comparable 

 in every way to a somatic character. 



8. All the genital and somatic peculiarities of the second group of 

 gynandromorphs are due to a mosaic arrangement of groups of cells 



