1056 



SUBMAMMALIAN VERTEBRATES 



The prairie rattler's reproductive system 

 includes, in anteroposterior succession, 

 ovary, oviduct, uterus, and vaginal pouch, 

 all of these being paired, and finally the 

 single cloaca. A careful study of sperm dis- 

 tribution during their storage in winter hi- 

 bernation showed that the germ cells are 

 concentrated in the anterior extremity of 

 the vagina and in the posterior end of the 

 uterus. It is believed that in the spring the 

 sperm migrate into the oviduct in order to 

 fertilize the eggs (Rahn, 1942; Ludwig and 

 Rahn, 1943). 



Live sperm can be demonstrated in a uter- 

 ine smear from the garter snake for a month 

 or more after mating (Rahn, 1940a). The 

 female garter snake stores sperm between 

 the uterus and the most anterior portion of 

 the oviduct (designated the infundibulum) 

 in a short, thick segment with specialized 

 alveolar glands. The latter communicate 

 with the oviducal cavity by branched, cili- 

 ated ducts. In this species sperm from a fall 

 mating spend most of the winter in disorgan- 

 ized masses in the oviducal cavity. In Feb- 

 ruary or March the germ cells move into the 

 lumina of the alveolar glands. Here in strik- 

 ing fashion the sperm are ranked side by 

 side, their heads against the alveolar epi- 

 thelium and their tails projecting into the 

 lumen. Finally, at ovulation, the sperm move 

 on to fertilize the eggs (Fox, 1956). 



Very little seems to have been published 

 on physiologic aspects of sperm storage in 

 reptiles. One wonders how the metabolic re- 

 quirements of the sperm are met for months 

 or years, how the sperm are guided to the 

 storage site, and how they are "released" at 

 the proper time. It seems safe to assume that 

 these processes are at least partly under the 

 control of sex hormones. This is an area 

 much in need of study. 



XVIII. Oviparity and Ovoviviparity 



Oviparous animals release their eggs to de- 

 velop outside the body. In ovoviviparous 

 animals, fertilization is internal, and the 

 embryo undergoes at least part of its devel- 

 opment within the mother. However, in this 



months (Trapido, 1940); Thamnophis sirtalis, 

 several months (Rahn, 1940a; Blanchard, 1942); 

 Tropidoclonion lineatutn, probably throughout 

 winter (Gloyd, 1928; Force, 1931); Xenodon mer- 

 remi, 1 year (Graber, 1940). 



case the fertilized ovum acciuires a definite 

 investing membrane or shell. There is enough 

 yolk for the nutrition of the growing embryo 

 so that no food materials need be supplied 

 by the mother. In viviparity at least part of 

 the embryo's nourishment is of maternal 

 origin. Intermediate stages also exist. The 

 evolution of viviparity is ably discussed by 

 Harrison Matthews (1955). 



Fish 



Oviparity of course is common. Ovovivi- 

 l)arity also occurs (see, for example. Turner, 

 1937a; Hisaw and Albert, 1947) ; in poecihid 

 fish the embryos develop within the follicles 

 and maintain gas exchange with the mother. 

 Because more than one (sometimes up to 

 nine!) brood, each of a different age, may 

 develop in the same ovary, a kind of super- 

 fetation exists (Turner, 1937a, 1947). 



Aittphibidns 



Nearly all amphibians are oviparous. A 

 few salamanders, including Oedipus, Hydro- 

 mantes (Noble, 1931), and Salaniandra 

 (Bay lis, 1939) , bring forth living young and 

 are regarded as oA'oviviparous. 



Reptiles 



Reptiles, (lei)en(ling on species, may be 

 oviparous, ovoviviparous, or viviparous. 

 Oviparity has been reported, for example, 

 for lizards of the genera Amphibolurus, Ly- 

 gosoma, and Egernia (Weekes, 1934). Phry- 

 nosoma cornutum, the horned toad, is ovipa- 

 rous, whereas P. douglassi is viviparous 

 (Edwards, 1903). Hemidactylus flaviviridis, 

 the Indian house gecko (Mahendra, 1936), 

 and Anniella pidchra, the American legless 

 lizard (Coe and Kunkel, 1905) are ovovivip- 

 arous. Jacobi (1936) has described in detail 

 the reproductive anatomy of the ovovivipa- 

 rous lacertilians Lacerta agilis and Anguis 

 frag His. 



Some snakes, the turtles, and the croco- 

 dilians bury their eggs or lay them in nests 

 for extended incubation. Other snakes ap- 

 pear to be ovoviviparous, i.e., the egg is well 

 supplied with yolk and acquires a shell, but 

 is retained in the oviduct for at least part of 

 the incubation period. Examples are Trachy- 

 boa (Barbour, 1937), the colubrid snakes 

 Xatri.r and Thamnophis (Bragdon, 1946),. 



