86 THE ORIGIN OF GYNANDROMORPHS. 



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the right side is male, the left imperfectly developed, a tendency towards the 



female type The internal genital organs were, as far as is known, 



imperfectly developed male organs." 



A theoretical explanation of the case, based on the chromosomal 

 peculiarities of the line, is as follows : Since practically all eggs had but 

 one Z chromosome before polar-body extrusion and lost it at their 

 formation, few males arise as Doncaster has shown, and even if Z 

 should exceptionally remain in a ripe egg it would carry the gene for 

 grossulariata; hence any male coming from it would be grossulariata. 

 Only then by the sperm bringing two Z's into a Z-less egg could a 

 lacticolor male arise. Such an abnormal sperm could arise in any 

 male by primary non-disjunction, or by secondary non-disjunction 

 from a ZZW male, i. e., by the two Z's of the spermatogonia both 

 passing to the same pole at one of the maturation divisions. If this 

 happens, a lacticolor male is expected. The appearance of femaleness 

 in certain parts of the left side must, then, be referred to an elimination 

 of one of the Z's at some early division. 



Doncaster's second case can be explained as a simple case of chromo- 

 somal elimination. A grossulariata female, by lacticolor male, gave 

 11 grossulariata males + 11 lacticolor females + 1 gynandromorph 

 whose anterior parts are male (including the wings to some extent), 

 and whose posterior parts are female. Here the normal proportion 

 of males to females, and the expected distribution of color to them, 

 shows that the female was normal as to her chromosomes. If we 

 assume, then, that a Z-bearing egg was fertilized by a normal Z-bearing 

 sperm, the result should be a normal grossulariata female heterozygous 

 for lacticolor. Elimination of one of the paternal Z's would give a 

 grossulariata male in the anterior region coming from the ZZ nuclei 

 and a grossulariata female posterior part coming from the single Z 

 nucleus. The second case is comparable in every way with the cases 

 of Drosophila and allows an extension of the theory of chromosomal 

 elimination to the group of moths, in line with the other critical cases 

 described above. Doncaster's first case must also appeal in part to 

 the same hypothesis, but it is more complicated, since another 

 exceptional phenomenon must have first occurred. This first process 

 gives a lacticolor male when a grossulariata male or no males at all are 

 expected. It is only that elimination later happened to take place 

 in this individual that it comes to be considered in this connection. 

 In other words, there is no necessary connection between the two 

 events, so that the non-disjunction phenomenon does not in reality 

 complicate the elimination explanation. The two are quite inde- 

 pendent. It should be pointed out that such exceptional males due to 

 non-disjunction are known to occur in Abraxas. 



Another gynandromorph in Abraxas (Tutt, 1897) involves varieties 

 A. ab. suffusa and A. ab. obscura. Since the genetic relation of these 



