COLD-BLOODED VERTEBRATES 



10(55 



(listingiii!shal)le in moi'iihology, location, and 

 function from the testis of a typical male. 

 The process of reversal may re(iuire 3 or 

 4 months. 



It is possible that co))i})lete adult sex re- 

 versal is more common than is realized. Un- 

 less by observation or autopsy it were 

 detected while in progress, or unless subse- 

 quent genetical studies could prove that sex 

 reversal had occurred, the phenomenon 

 might easily be unrecognized. 



The difficult question of the role, if any, 

 of the chromosomes in regulating sex re- 

 versal appears to be very imperfectly un- 

 derstood. Consideration of this and related 

 genetical problems is outside the scope of 

 this chapter. 



Amphibians 



See chapter by Burns. 



Reptiles 



Cases of postembryonic retention of het- 

 erosexual accessory structures and of her- 

 maphroditism in reptiles are summarized in 

 Table 17.2. The conditions described for 

 Hatteria {Sphenodon) (Osawa, 1897) ap- 

 parently, and for Malaclemmys (Risley, 

 1941b) and Alligator (Forbes, 1938b, 1940b) 

 definitely, are normal rather than excep- 

 tional. 



One of the most remarkable cases was 

 that of Hansen's (1943) turtle. Histologic 

 sections showed two ovotestes. The anterior 

 and posterior extremities of each gonad 

 were testicular and contained seminiferous 

 tubules. The central ovarian portion con- 

 tained mature and immature eggs. Vasa 

 efferentia joined the testicular areas to the 

 epididymides. The latter contained sperm, 

 and were connected by vasa deferentia to 

 the cloaca. There were two normal and aj)- 

 parently functional oviducts and a normal 

 penis. External characteristics were mascu- 

 line. 



Tayler's hermaphroditic lizard (1918) 

 had bilateral ovotestes with ova, seminifer- 

 ous tubules, and interstitial tissue. Epididy- 

 mides were normal except for the absence 

 of sperm and of vasa efferentia. Oviducts 

 were incomplete, and there was a penis. 



The writer (Forbes, 1940b) has described 

 the medullary "rest" at the j^iosterior end of 



each ovary in the immature alligator. The 

 rest is composed of medullary cords con- 

 taining germ cells. The cords may have 

 lumina. Rete canals join the medullary tu- 

 bules to a persistent mesonephros, the duct 

 of which extends to the cloaca. The female 

 thus seems to have potential testicular tis- 

 sue served by a complete excurrent system. 

 The medullary rest is bilateral but is quite 

 similar to the vestigial right gonad of the 

 hen (Erode, 1928) ; the latter contains germ 

 cells for three weeks after hatching. Rete 

 tubules and a right mesonephros and meso- 

 nephric duct also occur in the hen. 



Retention of heterosexual gonoducts is 

 not unusual. For an unknown reason, in 

 such cases all or nearly all of the meso- 

 nephric duct persists, whereas only part of 

 the ]\Iullerian duct is retained. 



XXill. Experimental Sex Reversal 



Fish 



Some effects of androgens and estrogens 

 on gonoducts, coloration, and other acces- 

 sory sex structures have been described. 

 Attention will now be directed primarily to 

 the effects of administered sex hormones on 

 the gonads themselves and to the sex-re- 

 versing action of castration. 



When the fighting fish, Betta splendens, 

 was ovariectomized, a testis regenerated 

 from the severed end of the oviduct in 7 of 

 150 spayed fish (Noble and Kumpf, 1937). 

 In time the 7 fish showed male fins, sperma- 

 togenesis, male behavior, spawning, and fer- 

 tilization of eggs. Nine males and 12 females 

 from these matings grew to maturity. If 

 males, on the other hand, were castrated, 

 they always regenerated testes. 



Testosterone propionate influenced the 

 genital ridge and accessory sex structures 

 in the elasmobranch Scyliorhinus to develop 

 in the female condition (Chieffi, 1954). The 

 same compounrl when given to female 

 Fhoxinus minnows caused ovarian disinte- 

 gration and the appearance of mascu- 

 linization pigment (Bullough, 1940b). In 

 Xiphophorus feeding (by adding it to 

 aquarium water) of testis powder or testos- 

 terone propionate to pregnant females and 

 to the young when they were born had the 

 result that all the young which grew to 



