FOUNDATIONS FOR SEX 



49 



most strains of chickens. A greater loss 

 would be expected for truly homozygous 

 chickens or poults as birds are known for 

 the large numbers of sublethal genes they 

 carry. In fact, it is surprising that any sur- 

 vive to the adult stage. 



The doubling of the W and A type would 

 result in individuals lacking the Z chromo- 

 some. From what was observed in Amphibia 

 and fish the WW + 2A, individual if it 

 survived, would be expected to be female. 

 Since this type has not as yet been detected 

 it may be inferred that it is inviable be- 

 cause of loss of certain essential genes in the 

 Z chromosome. 



X. Sex Determination in Mammals 



A. GOAT HERMAPHRODITES 



Goat hermaphroditism as reported by As- 

 dell (1936), Eaton (1943, 1945) and Kondo 

 (1952, 1955a, b) is of particular interest 

 when comjjared with human hermaphrodit- 

 ism as observed by Overzier (1955) and of 

 testicular feminization as reported by Ja- 

 cobs, Baikie, Court Brown, Forrest, Roy, 

 Stewart and Lennox (1959) and others. 

 In each species the phenotypic range in sex- 

 ual development extended from nearly per- 

 fect female to nearly perfect male, with the 

 most frequent class as an intermediate. Ex- 

 ternal appearance of each was partially cor- 

 related with internal structure. When inter- 

 nal female structures as the INIiillerian ducts 

 were present, the external appearance was 

 more female-like. When the male structures 

 AVolffian ducts were developed, the external 

 api^earance was more male-like. The pres- 

 ence of the dual systems within certain of 

 these hermaphroditic types indicates, as in 

 Drosophila, that there is independence of 

 development of each system without a so- 

 called turning point calling for differentia- 

 tion of the female sex followed by that of 

 the male sex or vice versa. 



In goats the hermaphroditic types were 

 traced to the action of a recessive autosomal 

 gene (Eaton, 1945; Kondo, 1952, 1955a, b). 

 This gene apparently acts only on the fe- 

 male zygote. In homozygous condition the 

 eml)ryos bearing them develop simultane- 

 ously toward the male as well as toward the 

 female types. This development resembles 

 closely that of the Hr gene in Drosophila, 



because, although Hr is dominant and the 

 one in goats is recessive, they both operate 

 only on the female type and both tend to 

 develop jointly both male and female sys- 

 tems in sexual development. 



One jarring note comes in relating the 

 cytologic basis for sex determination in 

 goats with that for the intersexes. The sex 

 ratios for the different crosses clearly place 

 the hermaphrodites as genetic females ex- 

 pected to have the XX chromosome con- 

 stitution. The XX constitution would then 

 also agree with that found for human 

 hermaphrodites as discussed later in this 

 paper. Makino (1950) has shown for one 

 case of the intersexual goat that its sex 

 chromosomes were of the male type. Ma- 

 kino's excellent studies with other species 

 made this observation of particular signifi- 

 cance as it was contrary to the other mor- 

 phologic and genetic evidence on these 

 hermaphrodites. The implications were fully 

 realized by Makino when the cytologic ob- 

 servations were made so that as far as pos- 

 sible the observations should be critical on 

 this point. However, there are several 

 sources of cell variation that suggest the 

 desirability of further checks. The chromo- 

 some number of the goat is large, normal 

 mitoses rarely appear in the gonads of the 

 intersexes, and the chromosomes of the 

 goat's spermatogenesis are so small as to 

 make difficult details of structure or identi- 

 fication. Some of the difficulties possibly 

 could be avoided by making tissue cultures 

 and determining the somatic chromosome 

 numbers of their cells. 



Kondo (1955b) has shown that under the 

 breeding conditions of Japan when the sire 

 was heterozygous, the percentage of inter- 

 sexes actually approached the expected 

 value 7.3 per cent. When the sires were 

 homozygous recessive individual matings 

 showed 14.6 per cent hermaphrodites as was 

 expected. Continued mating of homozygotes 

 should show 25 per cent of the total kids 

 hermaphrodites, or the equivalent of 50 per 

 cent of the female progeny. 



Hermaphroditism in goats has a further 

 advantage in that the locus is apparently 

 linked closely to the horned or polled condi- 

 tion. The horned condition, in consequence, 

 becomes a valuable indicator marking the 

 presence of the hermaphroditic factor in the 



