COLD-BLOODED VERTEBRATES 



1041 



storage. Readers interested in the detailed 

 anatomy of the hzard eiiididyniis arc re- 

 ferred to the accounts of Alverdes (1926, 

 1928). 



There are no true seasonal changes in 

 the ductuli effcrentes (tubules connecting 

 testis and epididymis) of the viper, Vipera 

 berus (Vols0e, 1944). Each epididymal tu- 

 bule has high, secretory epithelial cells in 

 one portion and low, nonsecretory epithelial 

 cells in the other. Chromophilic secretion 

 granules accumulate in the apices of the 

 secretory cells at all seasons and are even- 

 tually released into the lumen of the tubule. 

 There seems to l)e no seasonal variation in 

 the quantity of granules. Epithelial cells 

 of the ductus epididymidis show consider- 

 able seasonal variation in height (low in 

 summer, high in winter) but little or no 

 secretory activity at any time. The ductus 

 deferens also lacks secretory activity. In the 

 garter snake, Thamnophis, epithelial cells 

 are low in April and May and high in sum- 

 mer, fall, and winter (Fox, 1952). 



Gampert ( 1866) first described what later 

 came to be called the sexual segment of the 

 metanephros. In the nephron of the com- 

 mon water snake, Tropidonotus natrix, a 

 special segment is interposed between the 

 distal convoluted tubule and the collecting 

 tubule. Tribondeau (1902) described a tube 

 intermedaire in the kidneys of T. viperinus 

 and in Vipera aspis. He called attention to 

 the segment's distinctive secretory granules 

 and speculated as to its function. Later it 

 was determined that in Tropidonotus, Col- 

 uber {Zamenis}, and Vipera, the segment in 

 question is not the last but next to the last, 

 or preterminal, preceding the final portion 

 of the nephron which in turn empties into 

 the collecting tubule (Regaud and Policard, 

 1903a, b, c, d). Cells from the segment 

 could be kept alive in vitro for 3 days in 

 salt solution and could be stained supra- 

 vitally. In some tubes, the cells were accu- 

 mulating granules, whereas elsewhere gran- 

 ules were being discharged. It was further 

 noted that a large preterminal segment oc- 

 curs in male but not in female Lacerta and 

 Anguis. The term segment sexuel was 

 therefore applied to the structure. Finally, 

 it was discovered that the sexual segment 

 shows seasonal variations at the same time 



as does the testis, bespeaking androgenic 

 control. 



Many studies have since been made of 

 the sexual segment in lizards. General 

 agreement emerges that its epithelial cells 

 in the adult male become so tall during the 

 breeding season that the segment is macro- 

 scopically hypertrophied. The apices of the 

 cells are crowded with protein-like secre- 

 tion granules which push the small round 

 nucleus to the base o^the cell.'' In Taky- 

 dromus, not only the sexual segment but 

 the terminal segment, collecting tubules, 

 and even the ureters of the adult male are 

 lined with epithelial cells showing conspic- 

 uous secretory activity during the breeding 

 period (Takewaki and Fukuda, 1935a). 



Among adult male snakes, the pretermi- 

 nal segment lacks seasonal variation in 

 Natrix {Tropidonotus) and Thamnophis 

 (Eutenia) sirtalis but does show seasonal 

 secretory activity in T. r. radix, T. elegans 

 terrestris, and Vipera.^*' 



Curiously enough, the sexual segment has 

 not been found in turtles (Regaud and Po- 

 licard, 1903c, d; Herlant, 1933). Informa- 

 tion is lacking to as to a possible sexual 

 segment in the Crocodilia. 



VI. Intromittent Organ 



Fish 



In viviparous fish, sperm are transferred 

 to the female, at least in some species, 

 with the aid of an intromittent organ. Male 

 elasmobranchs have modified pelvic fins 

 which are used as "claspers" during copu- 

 lation. The further modification of the 

 clasi)er as a phallus-like organ for internal 

 fertilization has been described in Scijlliiim, 

 Acanthias, Raia (Leigh-Sharpe, 1920), and 

 Cetorhinus (Harrison Matthews, 1950). 

 The specialization of this organ in the 

 frilled shark, C hlamydoselachus anguineus, 

 is remarkable. The male discharges into a 

 groove on the medial side of the clasper a 

 mixture of sperm from the urogenital pa- 

 jiilla and sea water from the siphon sacs. 



"Zamik, 1910; Reiss, 1923b; Dornesco, 1925; 

 Cordier, 1928; Courrier, 1929; Matthev, 1929; 

 Kelil, 1935, 1944b; Regamev, 1935; Forbes, 1941; 

 Reynolds, 1943; Fox, 1958. 



'"Coi-dier, 1928; Waters, 1940; Takewaki and 

 Hatta, 1941; Vols0e, 1944; Fox, 1952. 



