1040 



SUBMAMMALIAN VERTEBRATES 



This pattern is somewhat modified in dif- 

 ferent genera. In Rana and Alytes (Noble, 

 1931), and in Eurycea (Weichert, 1945) 

 and Triton (Aron, 1924b), the terminal 

 part of the mesonephric duct is distended 

 by accumulated sperm and thus functions 

 as a kind of seminal vesicle. 



Reptiles 



In all the amniotes, the mesonephros is 

 eventually supplanted as a urinary organ by 

 the metanephros, or permanent kidney. The 

 mesonephros, however, is immediately ad- 

 jacent to the gonad and in the adult male 

 serves as a collecting and conveying mech- 

 anism for the mature germ cells. In rep- 

 tiles a few rete tubules or canals join the 

 terminal ends of the seminiferous tubules 

 to some of the mesonephric glomerular 

 capsules; in many lizard species the rete 

 canals are reduced to one (Alverdes, 1926, 

 1928; Regamey, 1935). The glomeruli them- 

 selves disappear after they cease to func- 

 tion, but the excurrent i)athway i)rovided 

 by the mesonephric tubules and the meso- 

 nephric duct persists, affording the sperm 

 a continuous route into the cloaca. In the 

 adult reptile, as in higher vertebrates, the 

 mesonephros is often referred to as the epi- 

 didymis, and the mesonephric duct as the 

 vas deferens. 



V. Secretory Specializations of the 

 Mesonephros and Metanephros 



Fish 



Fishes lack the metanephros of the am- 

 niotes. Instead, most of the mesonephros 

 continues to function as a kidney. The an- 

 terior end of the mesonephros may be mod- 

 ified in the male as a collecting organ for 

 the sperm. In various species of stickleback 

 {G aster osteus) a further and very inter- 

 esting specialization has occurred. The male 

 cares for the young. One of his functions 

 is to build a nest, collecting and assembling 

 plant debris, and sticking it together with 

 a special secretion, a kind of waterproof 

 cement. In the spring, as the time for nest- 

 building approaches, the diameter of the 

 tubules in the secretory portion of the mes- 

 onephros increases considerably. The epi- 



thelial cells of the tubules become three or 

 four times as tall as before and fill with 

 eosinophilic secretory granules which liqu- 

 efy to produce the glutinous cementing 

 substance for nest-building. This specializa- 

 tion does not occur in the female.'^ 



Amphibians 



Elevated, granule-filled epithelial cells 

 lining the mesonephric collecting tubules 

 and duct are a male sex character in Triton 

 alpestris and T. cristatus (Aron, 1924bj. 

 Their function is not apparent. 



Reptiles 



Cyclic changes in the height and ap- 

 parent secretory activity of the epithelium 

 investing the epididymal tubules have been 

 noted repeatedly (van den Broek, 1933). In 

 the turtle Terrapene (Cistudo), epithelial 

 cell height rises steadily from 14.5 fx in Feb- 

 ruary to 37.6 /x in July, declining thereafter 

 to 11.8 fji in October. The increase in cell 

 height correspondingly reduces the internal 

 diameter of the tubule (Dornesco, 1926b). 



Van der Stricht (1893) apparently was 

 the first to note the glandular nature of the 

 epididymal epithelium of a lizard, Lacerta 

 vivipara, and of the legless lacertilian, An- 

 guis fragilis. In Lacerta, Hemidactylus, and 

 Anguis there are four well defined seasonal 

 periods for the epithelium lining the epi- 

 didymal tubules: repose (autumn and win- 

 ter), presecretion (February and March), 

 secretion (April to June), and reconstruc- 

 tion (late June and early July). During the 

 secretory phase tlic tul>ules are distended 

 with a milky liciuid containing sperm 

 (Henry, 1900; Reiss, 1923b; Regamey, 

 1935). Secretory activity has been observed 

 during the breeding season in the epididy- 

 mides of lizards.^ When an epididymis of 

 Takydromus was surgically isolated, the 

 contained sperm retained their activity for 

 at least 70 days. This finding implies the 

 possibility of prolonged epididymal sperm 



"Mobius, 1885; Borcea, 1904; Hess, 1918; 

 Counier, 1921c, 1922a, b; van Oordt, 1924; Craig- 

 Bennett, 1931; Ikeda, 1933; van den Broek, van 

 Oordt, and Hirsch, 1938. 



^ Anolis (Fox, 1958), Emneces (Reynolds, 1943), 

 Hemidactylus (Dutta, 1946), and Takydromus 

 (Takewaki and Fukuda, 1935a). 



