128 " Gynandroinorphistn " and Kindred Problems 



with nuclei of different chromosome content. This was due to a similar 

 arrangement of the embryonic cells from which the different parts 

 developed. 



9. This arrangement of the embryonic cells is made possible by 

 the syncytial nature of the ovum in its cleavage and preblastodermic 

 stage, which allows nuclear migration to take place to any extent. In 

 most cases little or no migration takes place, in others it is extreme. 



10. The fact that nuclear migration is usually slight accounts for 

 the fact that gynandromorphs approaching the halved condition are 

 much commoner than those examples which show a more or less fine 

 mosaic of male and female characters on both sides. 



11. In birds four halved gj'nandroniorphs and one almost perfectly 

 halved are known. This is due to the fact that from each cell produced 

 by the first cleavage one lateral half of the individual develops. Nuclear 

 migration is absent or very slight. 



12. In insects trophic changes, heat and parasitism for example, 

 may alter the chromosome constitution of the cells in a postembryonic 

 stage of development, and lead to the assumption of male secondary 

 sexual characters in a female. 



This phenomenon is quite different from the kind of gynandro- 

 morphism discussed in this paper. 



DESCRIPTION OF PLATES. 



PLATE XXI. 



Fig. 1. Heteroohroic gynandromorph. Heiueropliila abruptaria. Kight <f , ab. ij«;iHea(« 



Tutt; Left ? type. Pair of ab. bnmneata and of typical specimens to show that 



the colour segregation is not a sexual one. 

 Fig. 2. Heteiochroie Abraxas flrossulariata i . Right side type. Left side ab. jiiflrii. 

 Figs. 3 and 4. Gynandromorphism with segregation of type colour and aberrational 



colour limited to female sex. Melanargia galathea. Mixture of type <J with ? ab. 



lugens. Note that as is the rule upper and under sides do not correspond. 

 Fig. 5. Three gynandromorphous Anwrpha popiili of Newman's strain (?heredity by 



indirect descent). For diagrams uf dissections see pp. 98, 99 and 100. (") Pre- 



domiuantly s . (b) Predominantly ? . (c) Predominantly ? . 

 Fig. 6. Gynandromorphous Agriades corulon (Herts, race). Heredity, ? by direct 



descent. Dissected it proved to be a secondary somatic hermaphrodite 

 Fig. 6a. Heterochroic gynandromorph. Abraxas sylvata. Left side ? type. Bight 



side <f ab. paiUarioides. 



