768 



J. F. GUDERNATSCH 



portions increase. The posterior end of the gland is found behind 

 the second gill branches. 



The follicles are usually circular or oval in cross sections, though 

 many are polygonal from pressure. Their size varies between 30 

 and 350/x medium sizes being most abundant. Giant follicles 

 reach 800/i long by 400/i in short diameter. Many follicles are 

 without colloid, while in others the colloid is much more shrunken 

 than usual. The colloid is homogeneous. The follicular epithe- 

 lium is of high cylindrical cells or cubical ones. The cytoplasm is 

 stained more darkly in the basal portions ; in the higher parts it is 

 sometimes reddish. The blood supply is rich. 



Fig. 13. Sections through the thyreoid gland of Pomatomus. A, anterior to the 

 aortic bifurcation; B, between the second and third branchial arteries. 



POMATOMUS SALTATRIX L. 



Young bluefish 30 cm. long. In this species the dispersion of the 

 thyreoid follicles is prevented in both a lateral and dorso-ventral 

 direction, since the arch formed by the basibranchiale and hypo- 

 branchialia is very narrow (fig. 13). The gland is thus a long 

 narrow streak (pi. I, fig. 11). At the aortic bifurcation there are 

 only a few follicles, some of which lie close to the first gill arteries, 

 just in front of their point of union. The thyreoid mass reaches its 

 maximum extension above the ventral aorta and between the 

 first and second gill arteries, especially towards the second. But 



