114 THE ORIGIN OF GYNANDROMORPHS. 



(6) In Abraxas a factor involved is known to be sex-linked. 

 Two mosaics between A. grossulariata and lacticolor described by 

 Doncaster can be accounted for by chromosomal elimination in one 

 case and by a non-disjunctional sperm and elimination in the other. 



(c) The two gynandromorphs in silkworms described by Toyama 

 can be explained, genetically, on the basis of two nuclei present in the 

 eggs. Doncaster has found such eggs in Abraxas. 



(d) Whether the mosaics in the gipsy moth, formed by racial crosses, 

 are due to different sex-factors having different quantitative value, 

 as maintained by Goldschmidt, or due to some other relations, seems 

 uncertain from the evidence so far published. 



(16) In reviewing the literature it is pointed out that in the Crus- 

 tacea and molluscs there are several cases where an individual is 

 male at one period of its life and female at another, just as some plants 

 pass through similar stages. In such cases the environment, taken 

 in the widest sense, may suppress one sex and develop the other. The 

 influence of the environment is clearly shown in the case of the crabs 

 infected by Sacculina, where the secondary sexual characters are changed ; 

 and in Crepidula, where proximity to another individual effects a 

 change of sex, and in the worm Bonellia, where a similar change is 

 brought about. There is nothing here that is in the least inimical to 

 the view that in other cases, and even in these same groups, there 

 may be genetic factors that determine sex under ordinary or other 

 circumstances. The bilateral gynandromorph of the crayfish (p. 97) 

 may be a case in point. 



(17) A few cases of bilateral gynandromorphs in birds have been 

 reported. Their occurrence is unexpected because of the known effect 

 of the ovary in suppressing most of the secondary characters of the 

 male. It is suggested that in some species of birds, particular secondary 

 sexual differences are not influenced by internal secretions, hence a 

 gynandromorph condition in the chromosomal composition might show 

 itself in plumage characters. It is also suggested that if a bird showed 

 the female complex in one region and a male complex in another the 

 amount of internal secretion that might inhibit one side might be in- 

 sufficient to inhibit the other. A transient or an abnormal condition 

 of the ovary might make the gynandromorph differences visible. 



(18) In man and in other mammals a number of cases of gynandro- 

 morphs are known, some of them at least well authenticated. Most 

 of the cases rest on the condition of the gonads and accessory sexual 

 organs. Sex mosaics like those of Drosophila are expected, because 

 the mechanism of sex determination is the same. On the other hand, 

 in the light of Lillie's evidence for the freemartin, other kinds of modifica- 

 tions may be possible. Even in cases where only a single individual is 

 born an earlier connection with an absorbed or aborted embryo might 

 be responsible for an abnormal condition of the sexual organs. 



