1070 



SUBMAMMALIAN VERTEBRATES 



stranded in moist plant debris three months 

 after flooded lowlands had dried up, were 

 placed , in tap water. Normal hatchlings 

 emerged from the eggs in 15 to 30 minutes 

 (Harrington and Haeger, 1958), another 

 instance of successful adaptation of the em- 

 bryo to an unfavorable environment. Ovar- 

 ian eggs of the dogfish, Squalus suckleyi, 

 contain estradiol-17/3 (Wotiz, Botticelli, 

 Hisaw, Jr., and Ringler, 1958). Estrogen 

 administration to Lebistes damages the 

 testis, inhibits ovogenesis, and is associated 

 with reduction in height of the epithelium of 

 the sperm duct and with enlargement of the 

 lumen of the ovarian excurrent duct 

 (Geske, 1956). Treatment of the goldfish 

 with estradiol was followed by a rise in the 

 serum level of total protein and of non- 

 ultrafilterable phosphorus and calcium, but 

 not, as in the bird, by concomitant hyperos- 

 sification (Bailey, 1957). 



In the selachians Torpedo and Sci/lior- 

 hinus the primitive gonad consists of both 

 cortex and medulla. During development, 

 the germ cells remain in the cortex if the 

 gonad is to become an ovary; if it is to be a 

 testis, they migrate to the medulla. In either 

 case, the gonad of the female is briefly bi- 

 sexual in appearance. The interrenal body 

 and gonadal medulla have a common origin. 

 As in birds, ovarian asymmetry appears to 

 be genetically fixed (Chieffi, 1950, 1952, 

 1955). Embryos of l)oth sexes of Scylior- 

 hinus have Miillerian ducts, but they per- 

 sist only in females (Thiebold, 1954). 



Two adult female Lebistes reticulatus 

 and one adult female Xiphophonis helleri, 

 individually and continuously isolated from 

 birth, gave birth to litters of 22, 14, and 28 

 young, all females. The mothers showed the 

 characteristic "pregnancy spot," a pig- 

 mented area near the base of the tail. Mi- 

 croscopic study of the gonads showed them 

 to be entirely ovarian and revealed the total 

 absence of sperm, ruling out the possibility 

 of self-fertilization by gametes from testic- 

 ular tissue. Parthenogenesis seems the only 

 other explanation. It is suggested that par- 

 thenogenesis may have resulted from stimu- 

 lation of the mature ova by the toxin of a 

 phycomycete with which all three mothers 

 were infected (Stolk, 1958). Ova were ob- 

 served in a testis of Barbus stigma (Sath- 



yanesan, 1957). True hermaphroditism has 

 been reported for the cutthroat trout 

 (Turner, 1946; Benson, 1958). 



Injection of testosterone propionate into 

 Scyliorhinus embryos was followed by hy- 

 pertrophy of the Wolffian ducts of females 

 and testicular inhibition in males. Treat- 

 ment of male embryos with estradiol 

 benzoate resulted in persistence and hyper- 

 trophy of the Miillerian duct and conver- 

 sion of the testis to an ovotestis. In a strain 

 of the medaka, Oryzias, the female is white 

 due to a recessive, sex-linked color gene 

 (X'"X''), whereas the male is orange-red due 

 to a dominant color gene linked to the Y 

 chromosome (X''Y^\). Thus color reveals 

 the genetic sex. If the third-generation 

 offspring of such fish were reared from 

 hatching to 8 months on a diet containing 

 estrone or stilbestrol, both the white and 

 the red fish were morphologically females. 

 (An exceptional red fish had both ovarian 

 and testicular tissue.) The red fish, geno- 

 typic males, clearly had undergone sex re- 

 versal. Normal diet had no effect on sex. If 

 the sex-reversed fish were mated to normal 

 males, they had normal offspring (Yama- 

 moto, 1953, 1957). If methyl testosterone 

 were fed, beginning at hatching, to the off- 

 spring of normal parents, development of 

 both testes and ovaries was inhibited. At 

 certain dosage levels of this androgen, fe- 

 male to male sex reversal also occurred 

 (Yamamoto, 1958). 



Beptiles 



Stefan (1958) studied immature male 

 and female tortoises, Eniys leprosa. Even 

 after hatching, testes still retained cortical 

 rests, medullary cords persisted in the ova- 

 ries, and Miillerian ducts were present in 

 both sexes. Treatment with androgens and 

 estrogens had little effect on the gonads, 

 presumably because their differentiation 

 was already too advanced. Both types of 

 hormone stimulated Miillerian duct growth, 

 and androgens caused phallic hypertrophy 

 in both sexes. 



XXV. References 



Ad.ams, a. E. 1940. Sexual conditions in Triturus 

 viridescens. III. The reprodiictii'e cycle of 

 the adult aciuatic form of both sexe.«. Am. J. 

 Anat., 66, 235-273. 



