THYMUS Ilf THE MARSUPIALS. 



551 



various lobes are uncouuected with each other save by looss 

 connective tissue. Lastly, there are the two large, lateral, 

 cervical lobes of the thymus (tm.c.) which have been described by 

 Symington, and which in my specimen were connected with the 



ih. 



^4 — 



Fig. 2. — Macropus Eugenii, pouch specimen. Diagram of the thyroid, thymus, 

 and associated structures. 



thyroid by the cord of cells (c.c), which resembled the latter in 

 histological structure. 



"With the exception of the lateral lobes of the thyroid, all these 

 structures lay ventral to the trachea {tr.). Ventral to all are the 

 submaxillary glands (sot.), delineated in outline. 



I am unable to say whether this peculiar connexion of cervical 

 thymus with lateral thyroid is peculiar to the family or only a 

 specific character. In the two other series of sections referred 

 to above it was absent. Possibly it may occur generally in the 

 development of the Macropodidse, though at different times, 

 and all my specimens were approximately of the same age. 

 But considered in the light of known facts of the development 

 of the neck-glands in the Mammalia, its presence is suggestive, 

 and points to the association in early development of the 

 cervical thymus and the lateral rudiments of the thyroid. 



In late years the development of these glands in various 

 mammals and in other classes of Vertebrata has been very 

 thoroughly worked out. It has been shown by de Meuron 



