124 " Giinandromorplimn" and Kindred Problems 



also unit characters and are probably carried by the same chromosome 

 as the sex factor itself, whilst ordinary somatic characters are borne by 

 the other chromosomes. 



In a normal union of sperm and egg nuclei fusion of the chromatin 

 takes place and at the subsequent cell division the nucleus of each 

 cleavage cell receives a similar amount of chromatin of the same kind. 

 But if the mitosis is an abnormal one or if the chromosomes of sperma- 

 tozoon or ovum were themselves abnormal, the division may not be an 

 equal one. 



The first cleavage cells may receive in the one case more chromatin 

 bearing maleness, and in the other more bearing femaleness, whilst 

 chromatin bearing the other characters may be equally distributed. In 

 this event an individual will be produced, in which all parts derived 

 from the one cell will be male in character and from the other female, 

 but that derived from either of them will be alike in somatic characters. 

 In other woi'ds it will be a halved gynandromorph. 



It is possible that this unequal division may affect only the 

 chromatin bearing the secondary sex character producing individuals 

 like the Hertfordshire coridoii, and similarly the other characters borne 

 by the chromosomes may be affected. 



The following unequal divisions may take place in insects : 



(1) Sex and secondary sexual characters, producing an ordinary 

 gynandromorph. Both these are usually affected together, because 

 probably they are carried in the same chromosome. 



(2) Secondary sex character only, producing a gynandromorph like 

 the Hertfordshire coridon (secondary somatic hermaphrodite). 



(3) Sex and sex-limited colour character like the gynandromorphs 

 in Dryas, half paphia male, haU valesina female. 



(4) Sex-limited colour only, producing heterochroic individuals 

 like the Colias, half edusa female, half helice female. 



(.5) A simple somatic character, producing heterochroic insects. 



(6) Sex and a simple somatic character, producing heterochroic 

 gynandromorphs. 



Of course all these phenomena could be explained equally well by 

 Lang's first hypothesis or by Doncaster's, but they would not explain 

 the case of homogeneous twins, one colour-blind and one with normal 

 sight. These must have arisen from the union of a single spermatozoon 

 with a single ovum, otherwise they would not have been identical in 



