304 



THE ELASMOBRANCH FISHES 



OVIDUCTS 



The oviducts in an immature female consist of a pair of slender tubes extend- 

 ing the entire length of the body cavity and emptying into the cloaca. They 

 take their origin by splitting off from the Wolffian duct (see fig. 257, od.) and 

 therefore retain the primitive funnel (fl., fig. 256) by means of which they 

 open anteriorly into the body cavity. Occasionally one of the oviducts is 

 rudimentary in the adult (Trygon). This in all probability is due to the 



Fig. 263. The 

 Waite.) 



A B 



shell of Heterodontus. A. E. francisci (orig.). B. H. gal eat us. (From 



crowding of the unusually large valvular intestine. In the adult the oviduct 

 is divided into several functional sections which may now be discussed. 



The oviducal funnel or the opening into the body cavity is formed as a 

 common aperture for the two oviducts (fl., fig. 251a). This is slit-like and is 

 lined with ciliated cells, the cilia of which may have something to do with 

 directing the eggs into the oviduct after they have reached the body cavity 

 from the ovary. Just below the funnel, in the part comparable to the fallopian 

 tube of higher forms, fertilization of the mature egg takes place. The egg then 

 passes downward to the area of the shell gland, where such exists, to receive 

 its shell. 



SHELL GLANDS 



The shell glands (s.g., fig. 253a) vary greatly in the different Elasmobranchs. 

 In Torpedo there are present in this region of the oviduct only a few strands 

 of granular tissue, which are incapable of producing a shell. In a type like 



