148 



DISCOVERY REPORTS 



series of embryo Eudyptes by Max Lewin (1903) and they apply equally well to the Ring 

 penguin. 



The cartilaginous skeleton at this stage is rapidly under- 

 going replacement by bone. Ossification of the chief ele- 

 ments of the axial skeleton is proceeding and to some extent 

 also replacement of the basic cartilages of the skull. 



The brain, with the completion of the cerebellum, takes on 

 the aspect and proportions of that of a typical bird. 



The eye, as shown in Plate VI, fig. 2, develops a large 

 pecten {pe) on its floor and the eyelids close. The pecten 

 in most birds is single, and it first arises in the penguin as a 

 simple lamellate process. By the time the embryo is ready to 

 hatch, however, this sheet of tissue is divided into ten units 

 (the teeth of the comb) which adhere to one another only by 

 their tips (Fig. 3 a). 



With regard to the viscera, the stomach lies on the left side 

 of the body and the much-coiled intestine is thrust dorsally Fig. 2. Left hind-limb, Gentoo 

 and to the right side of the coelomic cavity by the yolk sac. penguin embryo, stage 37 



. . . (Plate IV) 



The rectum opens into the cloaca, which receives the meta- 



nephric ducts (Plate VI, fig. 2, x), genital ducts (Plate VI, fig. 2,3'), and the bursa 



Fabricii. At the earlier stage (Plate V, fig. i) the bursa {bf) is a sac of large dimensions. 



It has dwindled in proportion very considerably by the time hatching is imminent. 



Rudiments of both gonads, with their ducts, are present in these later stages of the 



development, although in penguins, as in other birds, the right ovar}' and right Miil- 



lerian duct are atrophied in the adult. 



The large proportions of the gall bladder 



in relation to the liver is illustrated in Plate 



VI, fig. I, gh. It is rather puzzling to explain 



the excessive secretion of bile that this indi- 



It may be associated with the habit of 



cates. 



a b 



Fig. 3. Pecten from eye of Ring penguin embryo 

 on the point of hatching (Plate VI). a, elevation ; 

 b, plan. 



bringing large food supplies ashore in the 

 breeding season and of feeding the young 

 with partly digested chyme. To accomplish this the parents open their bills and the 

 young thrust in their heads as far as they can (Murphy, 1915, p. 120; Matthews, 1929, 

 p. 587). On the other hand, it may have a purely physiological significance. The food 

 taken is chiefly composed of Euphausians and Cephalopods. Both have a high per- 

 centage of fat, for the hydrolysis of which in large quantities during digestion an 

 abundant supply of bile salts may be necessary. 



In Plate VI, fig. 2, the lung is indicated by a dotted line and the blood vessels on the 

 dorsal side of it are drawn as if they were seen through it. It is interesting to note that 

 even at this late stage both right and left aortic roots remain in full operation in the 

 supply of blood to the dorsal aorta (Plate VI, fig. 2, ar). The persistent left umbilical 



