SPAWNING OF YELLOWFIN TUNA 



261 



The tubular diameter is about 0.20 mm. Within 

 this tubuh' lies anotiier tubule with a diameter of 

 0.0.5 mm. Circular transverse ridges on the wall 

 of the outer tubule give it a striated appearance. 

 Figure 4 shows a short section of a tubule that had 

 been teased from a mass. 



Histologically, these masses of tubules and eggs 

 are found to be surrounded by a connective tissue 

 stroma (fig. 5). The wall of the outer tubule 



seems to be composed of reticular connective 

 tissue. The wall of tlie inner tubule is made up 

 of a single layer of closely arranged minute cells 

 (3 M diameter) with relatively large, deep-staining 

 nuclei. 



The origin and function of these tubules are open 

 to question, but their pro.ximity to the residual 

 eggs suggests that they are involved in the 

 absorption of these eggs. 



[^DEVELOPING PORTION ^^DEGENERATING PORTION 



Figure 5. — Above: Part of section through ovary showing residual egg mass in xilir. c, connective tissue capsule; d. e., 

 developing egg; i. I., inner tubule; o. t., outer tubule; r. e., residual egg. Below: Diagram of this section, outlining 

 developing and degenerating portions. 



