COLD-BLOODED VERTEBRATES 



1051 



snakes on bio-assay contained the equivalent 

 of 200 estrone units i)er kilogram of fresh 

 ovaries (Valle and Valle, 19431. 



XIII. Oviduct; Egg Transport 



Fish 



According to Stronisten (1931), Rathke 

 (1824) discovered the oviduct of the fish. 

 This renowned old anatomist and embryolo- 

 gist also recognized that the oviduct is ab- 

 sent in the lamprey, Petromyzon, in the eel, 

 and in some salmonid fish, a deficiency since 

 noted in additional species (Brock, 1878; 

 MacLeod, 1881). In such fish the eggs are 

 released into the coelom and then reach the 

 exterior through an abdominal pore. As al- 

 ready stated, in most bony fish the ovary is 

 hollow, and the eggs or young pass succes- 

 sively into the ovarian cavity, oviduct, and 

 (in some viviparous forms) uterus. Informa- 

 tion is needed as to how the inert eggs are 

 moved. Eggert ( 1931 ) has concluded that 

 the oviduct is not homologous with the 

 Mullerian duct of higher vertebrates. 



The oviduct of the Japanese medaka, 

 Oryzias latipes, has been described in some 

 detail (Robinson and Rugh, 1943) , but there 

 is little information on seasonal variation in 

 the fish oviduct and on the role, if any, of 

 sex hormones in oviducal development. 



Amphibians 



In most and })erhaps all adult females, but 

 not in males or in inmiature females, the ven- 

 tral and lateral coelomic peritoneum is cili- 

 ated (Donahue, 1934; Rugh, 1935). The cilia 

 roll the liberated eggs into the ostium of the 

 oviduct, about two hours being reciuired for 

 the journey. If transplanted eggs or even 

 buckshot are introduced into any part of 

 the coelom, ciliary action will eventually 

 deliver them to the oviduct, although as 

 Rugh remarks, the heavy buckshot are 

 moved very slowly. 



The amphibian oviduct may increase in 

 size during the breeding season, then regress 

 (de Allende, 1939). The jelly-like coating 

 characteristic of extruded amphibian eggs 

 is contributed by oviducal glands. After ovi- 

 position this coating takes up water and 

 swells I Noble, 1931) to form a sticky layer 

 which protects the egg and often attaches the 



egg mass to underwater debris or even to the 

 adults in those species which transport the 

 eggs externally. 



Reptiles 



Lataste described in 1876 the histology of 

 the oviduct of a turtle, Cistudo [Terrapene) 

 europaea. The three layers of the ostium 

 consist of partly ciliated mucosa, connective 

 tissue, and investing peritoneum. The mid- 

 dle portion of the duct also has glandular 

 and muscular layers. In the final, or cloacal, 

 portion there are two muscle layers, and the 

 gland cells contain chromophilic granules. 

 Argaud (1920) saw both granule-producing 

 and mucin-producing gland cells in the ovi- 

 duct of an unidentified turtle. The oviduct 

 of the immature Testudo is lined with non- 

 ciliated cuboidal epithelium, and the epithe- 

 lium is also low in the sexually inactive 

 adult. During the breeding season the ovi- 

 duct is enlarged and the mucosa contains 

 muciparous cells interspersed among cells 

 in which the cytoplasm is crowded with 

 large secretion granules (Argaud, 1920; 

 Kehl, 1930). 



A classic study of the oviduct, including 

 that of the turtle Chrysemys, was made by 

 Parker (1931). He described longitudinal 

 pro-ovarian bands of cilia wiiich sweep the 

 sperm toward the ovary. Abovarian bands 

 of cilia beat in the opposite direction. If the 

 oviduct were opened longitudinally and par- 

 ticles of coal dust were scattered on it, both 

 types of band demonstrated their ciliary ac- 

 tion. Eggs, on the other hand, were believed 

 to be moved down the oviducts by peri- 

 stalsis. Van den Broek (1933) confirmed 

 Parker's observations regarding the regular 

 longitudinal folds of the mucosa. The former 

 states that the albumen of the egg is pro- 

 duced by the oviduct proper, whereas the egg 

 shell, the final investment, is secreted by the 

 "uterus" or last part of the oviducal tube. 

 Seasonal development of the mucosal cells 

 of the ostium occurs in Terrapene (Hansen 

 and Riley, 1941). In adult Emijs, on the 

 other hand, the mucosal cells do not change 

 throughout the year (Combescot, 1954b, 

 1955). 



The mucosa of the oviduct of Hatteria 

 (Sphenodon ) is folded and during pregnancy 

 is glandular in its terminal portion (Osawa, 



