TRANSACTIONS OF THE SECTIONS. 609 



The Brachyura being represented by the Land Crab, 



The Macrura Cray-fish, 



The Schi%opoda Mysis, 



rr,, ^ y. , r Gatnmarus a.ndPhro~ 



The Ampkipoda ^ „^-,„^^ 



The Loemodipoda Cyamus, 



The Isopoda ^ ^„^ Limnoria. 



The author, in conclusion, suggested that there might possibly 

 be some parasitic connexion between Zoii and the Crabs where- 

 by Mr. Thompson's statements might be accounted for, adding 

 that precisely analogous case exists in the young of the Cole- 

 opterous genus MeloS and the Pediculus Melittce. 



Observations on the Orbital Glands in certain tribes of Birds. 

 By P. J. Selby, F.R.S. ^c. 



In this paper, after adverting to the little attention hitherto 

 paid by natui'alists to these glandular bodies, or their supposed 

 use in the oeconomy of the birds in which they are found, the 

 author proceeds to point out their situation, &c., and to show 

 that they secrete an oily fluid of a peculiar quality, which fluid 

 is distributed, by appropriate ducts, over the eyes, and serves to 

 defend them from the action of the water, in which the birds 

 possessing the glands usually reside, or at least are in the 

 frequent habit of procuring their food ; that all birds be- 

 longing to the order Natatores, hitherto examined, possess the 

 glands, developed to a greater or inferior extent as their habits 

 are more or less aquatic ; that they are largest in the habitual 

 Divers, and in such as feed with the head submerged ; that they 

 also exist in many species of the order Grallatores, but only in 

 such as are well known to submerge the head in search of 

 food, by probing the sand &c. beneath the surface of the 

 water. After instancing several examples belonging to both 

 orders, and contrasting the size of the organ with the known 

 habits of the birds, he ftirther suggests that this oily fluid may 

 be more especially secreted to protect the eye from the effects 

 of saline or sea water, as the development of the gland appears 

 in a great degree to be regulated by the marine habits of the 

 birds, and that its mode of action is that of a thin and transparent 

 varnish spread over the globe of the eye. The structure and 

 form of the gland are then described, and the course of the ex- 

 cretory ducts pointed out. 



1834. 2 R 



