760 



J. F. GUDERNATSCH 



group consists only of small follicles which have traveled down- 

 wards along a vein running between the two halves of the muscle. 

 Further back the muscle bundles separate and here the greatest 

 mass of thyreoid tissue is found. The space between the pharynx 

 and bulbus is well filled by follicles which lie in a chaos of capil- 

 laries (pi. IV, fig. 7, Ca, F). 



Histologically this gland is as different from that in other spe- 

 cies as it is anatomicall)^ The gland, when fixed, may have been 



©V 



Fig. 9. Sections through the thyreoid gland of Siphostoma. 

 and B, posterior to the branchial arteries. 



A, at the second; 



in a peculiar state of function since there are no reasons to assume 

 that the histological structures observed are permanent. Coll<5id 

 was not found in any of the follicles, at least not as a uniformly 

 compact mass. Certain follicles contained highly acidophile 

 lumps about the size of epithelial cells. The epithelium, however, 

 seemed in a state of colloidalization. The cells were high, cuboidal 

 and swollen, with bulged out bases and surfaces (pi. IV, fig. 8). 

 The nuclei were centrally located or towards the lumen. Thus 

 they seemed to be typical colloid forming cells. The nuclei are in 

 some cases round and massive, usually however they are very 

 irregular. In some it seemed as though amitosis was taking place. 



