NECK GLANDS OF THE MARSUPIALIA. 361 



These are nearly all the forms examined. The results 

 obtained from several others (not included) are rather 

 doubtful, and renewed investigation is desirable. So far 

 as the facts go, they support the view suggested by 

 Symington, that the superficial cervical thymus is absent 

 in polyprotodont marsupials, as in all other mammalia in 

 which the anatomy of the neck has been investigated in 

 sufficient detail, and is characteristic of Diprotodontia. 

 The number of forms examined is still somewhat small, 

 and it is desirable that the possible presence of a cervical 

 thymic organ should be kept in mind in dissections of 

 marsupials. It has been seen that this structure may 

 enter into intimate association with the submaxillary 

 gland, and its presence may be overlooked where such 

 relations exist if the organs are not identified micro- 

 scopically. 



The morphology of the cervical thymus is obscure, and 

 until its development has been worked out in sufficient 

 detail little can be said as to its relation to the other 

 organs arising from the embryonic branchial pouches. 

 It appears probable that, like thymus and thyroid, it 

 arises from one or other of the posterior pouches. It is 

 now known that various other organs arise in connection 

 with the thyroid and thymus glands, and may enter into 

 variable relations with those structures. In connection 

 with the thyroid (itself a compound structure), there are 

 always two much smaller glandular bodies in association 

 with eadh lateral thyroid lobe. These are the " glandulse 

 parathyroids " of Sandstrom (epithelial corpuscles of 

 KJo'hn), and their development is now fairly well known.* 

 One of these bodies, the internal epithelial corpuscle 

 (" Glandule thyrodienne " of Simon) is always sunk in 



* See C. Simon, Thyroide lateralc et glandule thyroidienne chez les 

 mammiferes. Nancy, 1896. 



