E. A. Cock AVNE 123 



But one does not find any nice producing jin F^ generation, white 

 on one side and black on the other, even as an exceptional occurrence. 

 Yet this should be the case if Goldschmidt is correct. 



Again according to him inbreeding and crossing dititerent races oi- 

 species are the cause of all gynandroiiiorphisni, and it is certainly true 

 that many have arisen in inbred races. But in the inbred races which 

 have produced the heterochroic gynandromorphs there has been no 

 evidence to show that there has been any alteration in the potency of 

 the colour characters. They have remained completely dominant and 

 completely recessive in further generations, as in Simmons' abruptaria 

 The numbers too in most of these familial cases are too small to suit a 

 simple Mendelian expectation. 



The gynandromorphous birds and the case of twins published by 

 Nettleship can scarcely be explained on his theory. If the heterochroic 

 gynandromorphs arise as Goldschmidt and Poppelbaum believe, the 

 mosaic areas formed of the colour and pattern of the two sexes, and 

 those formed of the colour and pattern of the type and the variety, 

 would not be coterminous but would be independent. 



They seem to be coterminous in cases where any attention has been 

 paid to this point. 



Ltmg, in his second hypothesis, has suggested that a factor can be 

 lost in one or more somatic cells, or even in a sex cell. For instance 

 sex factors for the female {FG){FG){MA){MA) might by loss of a 

 factor become (;FG)(FG)(MA){tna), i.e. those of the male. If this 

 happened in one of the first cleavage cells, you would get a halved 

 gynandromorph, if later a coarsely or finely mo.saic-built gynandro- 

 morph. The weak point, as Poppelbaum points out, is the necessity for 

 supposing a very large number of simultaneous mutations of the same 

 kind in different cells in the mosaic gynandromorjjhs. 



The existence of individuals showing a mosaic of different sex and 

 colour, such as some of the heterochroic gynandromorphs, where each 

 sex and colour occupies exactly the same area.s, necessitates the supposi- 

 tion that a number of simultaneous mutations of two different and 

 independent kinds can occur in a number of cells, but that neither 

 mutation can occur in any cell without the other. For this to occur 

 more than once would be miraculous, and yet it must have occurred on 

 many occasions if Lang's hypothesis is true. 



The theory in which I believe is based on the supposition that sex 

 is a Mendelian unit character. The sex factor is probably carried by a 

 special chromosome. Secondary sexual and sex-limited characters are 



