COLD-BLOODED VERTEBRATES 



1087 



breeds in late March and tlie first part of 

 April. By the latter date, the store of ma- 

 ture sperm is exhausted. In June the masses 

 of spermatogonia in the testicular lobules 

 have begun to transform into primary sper- 

 matocytes. Spermatids are seen in late July, 

 and mature spermatozoa are present before 

 the first of September (Weichert, 1945). 

 Spermatogenesis in Necturus extends from 

 April through August, with shedding of 

 sperm from late August to early October. 

 Thereafter the testes are inactive until the 

 following spring (Aj^lington, 19421. 



The toad, Bujo bujo, breeds in the sjiring, 

 and the testes are largest then. Spermato- 

 genesis begins in the summer in preparation 

 for the next spring (Ting and Boring, 1939). 

 Sperm production is also cyclic in Rana 

 (Aron, 1926; van Oordt and van Oordt, 

 1955). 



Control of spermatogenesis has been 

 proven to be largely through the pituitary 

 gland (see chapter by Greep). Release 

 of spermatozoa has also been effected in 

 Rana by the injection of epinephrine, even 

 after hypophysectomy or total section of 

 the spinal cord. Bufo, however, did not make 

 this response to the administration of epi- 

 nephrine (Li and Chang, 1949). 



Except for two primitive families, all 

 salamanders enclose masses of their sper- 

 matozoa in sacs called spermatophores. The 

 latter are formed by specialized male eloacal 

 glands (Dunn, 1923; Noble, 1931) which 

 presumably are under endocrine control. 



Reptiles 



The organization of the reptilian testis 

 is in general like that of higher vertebrates. 

 True seminiferous tubules are present. The 

 period of active spermatogenesis is evident 

 on macroscopic examination, because the 

 testis increases in size as the germ cells 

 multiply and accumulate. In Testudo orbic- 

 ularis, the musk turtle, Sternotherus odo- 

 ratus, the box turtle, Terrapene carolinensis, 

 and the Algerian Emys leprosa, spermato- 

 genesis begins late in the spring and con- 

 tinues until early in the fall (Pellegrini, 

 1925; Risley, 1938; Hansen, 1939; Altland, 

 1951; Combescot, 1954a). These turtles 

 mate in the spring, whereas the musk turtle 

 mates in the spring and fall (Risley, 1938; 



Combescot, 1954b). In lizards, active sper- 

 matogenesis may, depending on the species, 

 take place at almost any time of year, 

 with a peak of spermiogenic activity, fol- 

 lowed by mating, appearing perhaps most 

 commonly in the spring and early summer.^ 

 In the snake, Thamnophis, spermatogenesis 

 begins late in the spring and is most active 

 in June and July. Spermiogenesis is con- 

 spicuous in August and October, and mat- 

 ing occurs in the spring (Cieslak, 1945; 

 Fox, 1952). Spermatogenesis is continuous 

 in Vipera berus except during hibernation, 

 and mating begins in late April or early 

 May (Volspe, 1944). The alligator ap- 

 parently breeds in the spring (Reese, 1915), 

 but information on the mating activities 

 and spermatogenesis in the Crocodilia is 

 surprisingly scanty. 



III. Sources of Male Hormone 



Fish 



Fish testes produce androgen. Hazlcton 

 and Goodrich (1937) and Potter and Hoar 

 (1954) prepared extracts of salmon testes 

 which when bioassayed showed male hor- 

 mone activity. (The effects of castration 

 will be described later.) Which testicular 

 cells produce androgen is controversial. In 

 the higher vertebrates, the interstitial cells 

 (Ley dig cells) are usually believed to se- 

 crete male hormone, and it was natural to 

 search for these cells in fish. Champy 

 (1923a, b) and van Oordt (1923, 1924, 

 1925) concluded that male hormone does 

 not come from interstitial cells in Tinea 

 indgaris, Pho.rinus laevis, Gasterosteus 

 pungitius L., and Xiphophorns helleri. 

 Courrier (19211)) and Wcisel (1949) did 

 not find interstitial cells either in primitive 

 elasmobranchs or in two teleost species. Such 

 cells have, however, been noted in the testes 

 of other species (Courrier, 1921b, 1922c; 

 Kolmer and Scheminzky, 1922a). Further- 

 more, interstitial cells undergo maximal 

 development (thus seeming to signal secre- 

 tory activity) just before and during the 

 breeding period; their presence may be 



'Pellegrini. 1925; Frankenberger, 1928; Cour- 

 rier, 1929; Altland, 1941; Breckenridge, 1943; Rey- 

 nolds, 1943; Dutta, 1944; Kehl, 1944b; Woodbury 

 and Woodbury, 1945; Miller, 1948, 1951; Kitada, 

 1951; De8.sauer, 1955; Fox, 1958. 



