FOUNDATIONS FOR SEX 



15 



this gene in the second chromosome. Price 

 ( 1949j placed the gene within the second 

 chromosome near the locus of "brick" by 

 inducing crossing over in males by expos- 

 ing them to x-rays. Newby (1942) exten- 

 sively studied the embryologic sequence in 

 development of the organs of these inter- 

 sexual types. The Ix^ gene did not affect 

 the males, XY 4- 2A, but did change the fe- 

 males XX + 2A into intersexes when it was 

 in the heterozygous condition. The intersex- 

 uals had 9 tergites; the first 6 were like 

 those in the normal female and the last 3 

 were small and irregularly formed. There 

 were 6 sternites, the first 5 being normal, 

 but the 6th malformed. Anal valves were 

 lateral as in the male but a third small 

 valve was also present at the ventral side 

 of the anus. The plates forming the claspers 

 were of irregular pattern and found ventral 

 to the anus. The vaginal plates were often 

 extruded into a genital knob and were be- 

 low the claspers. The knob occasionally be- 

 came heavily pigmented. The internal or- 

 gans ranged from nearly female through 

 those which were of hermaphroditic type 

 containing representative organs of both 

 sexes to individuals almost wholly male. 

 Newby concluded that intersexuality ex- 

 presses itself as a response to the develop- 

 mental pressures of both sexes, not as de- 

 velopment in the one direction followed by 

 a change. 



Gowen in 1940 established a stock carry- 

 ing the dominant gene Hr which had ap- 

 l)eared as a mutant in one of his cultures of 

 D. melanogaster. This gene affected diploid 

 females of XX + 2A type but not the males 

 of XY -I- 2A constitution. In the presence 

 of the Hr gene the diploid phenotype of the 

 females changed into a sterile type with 

 male secondary reproductive system associ- 

 ated with the female counterpart. The first 

 6 segments were complete with 6 spiracles. 

 The 7th was small with spiracle. The 8th 

 was small but without spiracle. Sternite 

 forming rudimentary ovipositor was usu- 

 ally protruded. Ninth and 10th segments 

 resembled those of males with large tergal 

 plates. Claspers were abnormal and had a 

 pair of small plates flanking the anus ma- 

 joi-ly in vertical position. Organs formed, 

 although sometimes modified or missing, 

 included: sex combs of 6.9 long slender 



teeth, gonads distinguishable from those of 

 the ordinary male or female in the 3rd and 

 possibly the 2nd instar, genital ducts male 

 and/or female, male accessory gland, penis 

 deformed, sperm pump, vas deferens, sper- 

 matheca, ventral receptacle often displaced, 

 and occasionally parovaria. The primary 

 gonads were often abnormal ovaries but in 

 rarer instances bore a crude resemblance 

 to testicular tissue. The yellow of the testes 

 was frequently present as material clinging 

 to the ovary. 



Superfemales with one dose of the Hr 

 gene had sex combs and developed parts of 

 both the male and female external and in- 

 ternal reproductive systems. Sex combs had 

 an average of 5 long and slender teeth. Ab- 

 dominal segment 8 developed as in the fe- 

 male, and formed the vaginal plate. The 

 latter was abnormal in shape, ordinarily 

 becoming a sclerotic protuberance. Seg- 

 ments 9 and 10 developed more as in the 

 male but were incomplete and abnormal. 

 The genital arch did not develop but the 

 inner lobe of tergite 9 showed irregular and 

 abnormal growth as for the claspers. Seg- 

 ment 10 developed, as in the males, into 

 longitudinal plates flanking the anus. The 

 internal genitalia were underdeveloped but 

 consisted of mixtures of male and female 

 organs. Gonads were rudimentary but gen- 

 erally consisted of a pair of ovaries with 

 small traces of yellow pigmentation. 



The triploid fly with one dose of the Hr 

 gene was largely female with developed 

 ducts, ovaries and eggs, but was sterile. The 

 male characteristics were small sex combs 

 and dark abdominal plates. In superfe- 

 males, sex combs were present and teeth 

 were intermediate between those of the dip- 

 loid female and triploid female. The gene 

 showed a dosage effect in triploids which 

 was less than that observed in diploids and 

 was in relation to the relative balance of 

 the gene with its normal alleles, 1:2 for 

 the triploid and 1 : 1 for the diploid. The 

 developmental effects of Hr as well as the 

 pigment producing potentialities of testes, 

 ovaries and hermaphroditic gonads have 

 been discussed by Fung and Gowen (1957a, 

 b). 



Hr has been shown to be allelomorphic to 

 a recessive gene, tra, described by Sturte- 

 vant (1945) and known to be located in the 



