694 THE PHYSIOLOGY OF REPRODUCTION 



of changing from a female to a male condition. The ovaries failed 

 to reach complete development, but discharged follicles and luteal 

 cells as well as fully formed spermatozoa are described. 



Bond l has given an account of a Formosan pheasant with unilateral 

 development of the secondary male characters and an ovo-testis on 

 the left side, and this bird he is disposed to interpret as having de- 

 veloped from a female zygote in which the sex-factor divided unevenly. 



Eiddle's experiments on sex-reversal in pigeons and doves have 

 already been referred to, and it was recorded that this investigator 

 obtained various grades of sexual individuals ranging from complete 

 males to complete females, in some of which the sex characteristics 

 might be over-emphasised as by the development of a right oviduct. 



Intersexual forms have been described in various insects and 

 notably by Goldschmidt 2 for the gypsy moth Lymantria. He 

 crossed two species of this moth, L. dispar and L. japonica, both of 

 which are strongly sexually dimorphic, and showed that with 

 suitable combinations of different races of these species " intersexes " 

 forming a continuous series passing from complete maleness to 

 complete femaleness could be produced. The results are ascribed 

 to different degrees of potency in the sex-factors, and thus a strictly 

 genetic interpretation was arrived at, but Goldschmidt's latest 

 results with sex-ratios, as Huxley remarks, indicate the probability 

 of moths with the chromosome constitution of one sex having been 

 changed into functional individuals of the other sex. 



Huxley refers also to Harrison's 3 results with another species 

 of moth, and to Keilin and Nuttall's 4 account of a graded series of 

 intersexual lice, as well as to the experiments of Hertwig and 

 others, and the records of Pearl and Parshley above mentioned, all 

 of which point in the same direction. 6 



It has already been mentioned that the Free-Martin has been 

 regarded as a partial hermaphrodite. Lillie 6 has shown that during 



1 Bond, " On a Case of Unilateral Development of Secondary Male Characters 

 in a Pheasant, etc.," Jour, of Genetics, vol. iv., 1914. 



2 Goldschmidt, " Experimental Intersexuality and the Sex Problem," Amer. 

 Nat., vol. 1., 1916. For a full account with references to many papers, see 

 Goldschmidt's book referred to above, p. 661. 



3 Harrison, "Genetical Studies in the Moths of the Geometrid Genus Oporabia, 

 etc.," Jour, of Genetics, vol. ix., 1919. 



4 Keili n and Nuttall, " Hermaphroditism and other Abnormalities in Pediculus 

 humanus" Parasitology, vol. xi., 1919. 



5 See also Banta, " Sex Intergrades in a Species of Crustacea (Simocephalus)" 

 Proc. Nat. Acad. Sci., vol. ii., 1916. Sturtevant, "Intersexes in Drosophila," 

 Science, vol. li., 1920. Sexton and Huxley, " Intersexes in Gammarus, etc.," 

 Jour, of Marine Biol. Assoc., vol. xii., 1921 ; and Bridges, loc. cit. (see p. 674). 



Lillie (F.), "The Theory of the Free-Martin," Science, vol. xliii., 1916; 

 " Sex-Determination and Sex-Differentiation in Mammals," Proc. Nat. Med. Sci., 

 vol. iii., 1917 ; "The Free-Martin : A Study of the Action of Sex-Hormones," 

 Jour. E.vp. Zool., vol. xxiii., 1917. 



