458 Genetics of Sex Determination 



saphila (Dobzhansky and Bridges, 1928; Dobzhansky, l9S0b; LebedefiF, 

 1939), Amphibia (Witschi, 1914 fF.), and, of course, all cases of the 

 freemartin type. This means for homologous anlagen that the anlage 

 changes its developmental path during development with the result 

 tliat the features laid down early are those of the primary sex, and 

 the later features are those of the new sex. The result is the 

 "mosaicism in time" of which so many beautiful examples have been 

 shown for the gonads and genital armature of Lymantria. The 

 developmental situation is, however, different for non-homologous 

 anlagen. In the normal sexes only one of the cell groups (male or 

 female) may develop at all (e.g., the imaginal disc for definite female 

 or male parts), while the cells at the other location do not form a 

 disc at all. After the turning point in intersexuality, the primarily 

 absent disc of the other sex begins to differentiate. The result would 

 be a rudiment of the organs of the primary sex and more or less 

 development of the organs of the other sex after the turning point; 

 the details depend upon the time of incidence of the turning point, 

 that is, the degree of intersexuality. In this case, however, the turning 

 point may occur at a time when the determination of the primary 

 disc is already final, which means that it continues differentiating in 

 spite of the turning point. The result is that more or less complete 

 organs of both sexes are present. Minor examples of this are found 

 in Lymantria; more extreme ones, in Drosophila diploid intersexes 

 (Lebedeff), and in the triploid intersexes of Solenobia. 



Finally, if the alternative is based upon primarily different an- 

 lagen, both present in either sex, as in Amphibia, different conditions 

 of development of both anlagen and different types of suppression of 

 the other result, as Witschi's work on frogs demonstrates. But in 

 vertebrates (see the work on birds and mammals reviewed by C. R. 

 Moore, 1944; Witschi, 1950; Ponse, 1949), the complicated interfer- 

 ence of hormones makes the details much more variable than in 

 insects. These, then, are the basic features of the morphological con- 

 sequences of genetic or induced intersexuality. 



The most elaborate work on the morphology of intersexes (apart 

 from Baltzer's work on Bonellia, which is not strictly comparable with 

 the material of the present discussion as analyzed in detail in Gold- 

 schmidt, 1931, 1938a, 1946fl, 1949Z?) is the work of Seiler and his 

 students (full literature in Seiler, 1949; and Ammann, 1954) with the 

 triploid intersexes of the moth Solenobia. It is unfortunate, in my 

 opinion, that this very elaborate and devoted work has led to inter- 

 pretations which cannot stand a critical scrutiny. For a long time 



