EXPLANATION OF PLATE V 



10 Salvelinus fontinalis, spec. no. III. Capillary network, Ca, around the 

 follicles. Note the highly columnar epithelium of the upper and the cuboidal 

 epithelium of the two lower follicles. Dia. 1 : 134. 



11 Salvelinus fontinalis, spec. no. II, showing different heights of the epithelial 

 cells in the same follicle. Dia. 1 : 375. 



12 Salvelinus fontinalis, spec.no. II. Distribution of the thyreoid elements and 

 their capillaries, Ca, in the connective and fatty tissue network. Dia. 1 : 64. 



13 Salvelinus fontinalis, spec. no. III. Much swollen colloid forming cells, 

 Coz, which have been cast off from the follicular wall into the colloid, Co. 

 E, epithelium; iV, nucleus; V, vesicles in the colloidal substance. Dia. 1: 650. 



14 Oncorhynchus. A general view of the thyreoid gland between the first and 

 second branchial arteries. Ph, epithelial floor of the pharynx; F, follicles surround- 

 ing the copula; A, ventral Aorta. Dia. 1: 60. 



15 Anguilla. A duct, D, connecting a small, /, and a large thyreoid follicle, F. 

 Dia. 1: 165. 



16 Anguilla. This photograph shows a complex of follicles which, on tracing 

 through the series, are found to connect with the follicle, F, on the right side of 

 the illustration. Dia. 1: 170. 



17 Cynoscion. A general view of the densely arranged follicles of this species. 

 Co, colloid; E, epithelium. Dia. 1: 165. 



18 Cynoscion. This picture shows the ramifying lymph spaces, L, completely 

 filled with the same substance as the follicles, F. Dia. 1 : 170. 



19 Tautoga. The epithelial wall, E, of the follicle, F, is cut somewhat tangen- 

 tially so that the network of anastomosing capillaries, Va, enclosing the follicles 

 can be seen. Dia. 1: 145. 



20 Clupea. Much swollen colloid forming epithelial cells, Coz, in a colloid 

 zone. Dia. 1: 170. 



21 Sarda. Showing smooth muscle bundles, M, invaded by thyreoid follicles. 

 Dia. 1:60. 



