152 JEREMIAH S. FERGUSON 



higher vertebrates. Possibly the thick tenacious secretion formed 

 by the endostyle, upon the presence of which the function of the 

 organ very largelj' depends, may well be taken to bear a relation 

 to the colloid material which is so characteristic of the mammalian 

 gland. Inasmuch as the retention of an albuminous secretion 

 within the glandular lumina of the animal body, a condition 

 frequently observed by the pathologists and normally present in 

 other glands as well as the thyroid, e.g., mammary gland, kidney, 

 hypophysis cerebri and parathyroid gland, leads to the accumu- 

 lation of a colloid material bearing a more or less striking resem- 

 blance to the colloid material in the follicles of the thyroid gland, 

 the deduction from the phylogenetic standpoint, that the reten- 

 tion within the follicles of the thyroid of a once free mucous se- 

 cretion would account for the colloid character of the follicular con- 

 tent, would not seem inappropriate. The character of cells 

 which pour forth the free secretion of the endostyle or h}q3obran- 

 chial thyroid of the Ascidians, Amphioxus and Cyclostomes is not 

 so very different from the colloid secreting cells of the thyroid 

 follicles of mammals. 



In the Teleostei, Wagner ('53) has studied the form and loca- 

 tion of the thyroid gland and directed attention to the similarity 

 of its structure to that of mammals. Simon ('44) and Baber ('81) 

 have given extended descriptions of the thyroid gland in several 

 species of bony fishes; Maurer ('86) described the structure and 

 studied fully the development of the thyroid gland of the carp 

 and trout. In the more recent literature the structure of the thy- 

 roid in fishes seems not to have received the attention which it 

 apparently deserves. 



Extended descriptions of the thyroid gland of reptiles are 

 found in the articles by Simon ('44) and Baber ('81). De Meuron 

 ('86) studied the organ in Lacerta. Van Bemmelen ('87) described 

 the gland in Hatteria and Lacerta as being transversely placed 

 over the trachea near the heart, and as forming a small, thin 

 unpaired organ. Guiard ('96) has also discussed the structure of 

 the organ in reptiles. 



In the Amphibia the work of Maurer ('88) and the excellent 

 descriptions by Wiedersheim ('04) apparently leave little to be 



