THYREOID GLAND OF THE TELEOSTS 729 



stages of activity. Here again we meet with difficulties since the 

 same folHcle sometimes shows high cylindrical epithelium on 

 one side and a flattened epithelium on the other (pi. V, fig. 11). 

 Hiirthle considers the flattening and stretching of the cells to be 

 the final stage in the process of colloid formation. He finds this 

 type of cells not sporadically, but always in the larger groups of 

 follicles. The low epithelial cells are still alive and accordirgto 

 Hiirthle may again transform into high ones. Biondi claims that 

 when the follicle has reached a certain size, the epithelium par- 

 tially flattens and vanishes, thus establishing a communication 

 between the follicular lumen and the lymph spaces and allowing 

 the colloidal material to be poured into the lymph system. The 

 emptied follicle is said to collapse and from its cell mass a new 

 follicle originates. Anderson, also, thinks that by a 'meltirg' of 

 the epithelium a connection is formed between the lymph space 

 and follicle, but the individual follicle is not destroyed. 



In the conger eel Baber finds oval cells between the cylindrical 

 ones and attributes to them the formation of new follicles, an 

 idea which I think is incorrect. The two classes of cells could not 

 be found in the common eel. Baber also finds in the conger eel 

 'club-shaped' cells between the epithelial cells. They are much 

 narrower than other cells and possess elongated nuclei. Their 

 free ends project above the general surface and are expanded 

 'fan-like;' the bases may also show a similar condition. Baber 

 regards them as branched cells, often existing in pairs, and form- 

 ing stomata which play an important part in absorption and secre- 

 tion. If this be true such cells should exist in all glands. I was 

 unable to find these and think perhaps they may have been con- 

 sequences of his alcohol preservation. 



The form of the nucleus changes with the form of the epithe- 

 lial cell. It is usually circular or somewhat oval in cross section. 

 When the cell is either cylindrical or flattened, the nucleus becomes 

 more and more elliptical in shape, with its long axis parallel to 

 that of the cell. Thus in the first case the long axis of the nucleus 

 is vertical to the free surface of the cell and in the second parallel 

 with it. When the nuclei are oblong in spite of the cells being 

 broad and cubical (for instance in some follicles of Muraneoides) 



