PRATT: REPRODUCTION IN BLUE SHARKS 



CRAINIAL OVIDUCT 



LUMEN OF OVIDUCT 



ALBUMEN SECRETING ZONE 





CENTRAL LUMEN 

 LAMELLAE 



SHELL SECRETING ZONE - 

 ANTERIOR HALF 



SHELL SECRETING ZONE- 

 POSTERIOR HALF 



CAUDAL OVIDUCT 



Figure 24.— Sagittal section of the oviducal gland in the blue shark i ^5 cross section). 



secreting zone. The mucus-secreting zone found in 

 some elasmobranchs is reduced or absent in the 

 blue shark, perhaps because of the limited shell 

 that is produced. Secretory tubules originate 

 blindly around the circumference of the gland and 

 extend inward, parallel to one another. In the 

 course of their travel they bow posteriorly for sev- 

 eral millimeters, then return to the latitude of 

 their origin where they communicate with the 

 central lumen. 



The albumen-conducting tubules enter the 

 lumen as a series of 13-15 evenly spaced lamellae 

 with irregularly flattened ends. The shell-secret- 

 ing tubules terminate in tufted pockets bordering 

 the central lumen. 



The posterior half of the shell-secreting section 

 communicates with the lumen through paired 

 caudal protuberances of secretory tissue (Figure 

 24). They are embedded in a stroma of connective 

 tissue and run a shorter, more irregular course to 

 the lower central lumen where they end in larger 

 and less uniform lamellae. 



As the gland matures the lumen branches into 

 two diverticula, which extend around its circum- 

 ference and into each lateral horn in a medial cross 

 section. These two diverticula give the lumen a 

 symmetrical S-shaped appearance (Figure 1.3i. 



Of those sharks studied by Prasad ( 1944, 1945, 

 1948), the oviducal gland of the blue shark most 

 closely resembles that of Carcharhinus dus- 



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