144 DISCOVERY REPORTS 



Visceral clefts III and IV still visible at the surface, numbers I and II enclosed by the 

 overlapping hyoid arch (hy) which extends upwards close to the otocyst. 



Umbilical stalk complete. Yolk duct opens into the intestine. Allantois well developed. 



Liver bilobed : a conspicuous organ lying close to the base of the heart and occupying 

 a large share of the available coelomic space. 



Lungs pvriform. They are still simple sacs with a wide central cavity forming the main 

 intrapulmonary bronchus (the mesobronchus). At this stage the mesobronchi are be- 

 ginning to bud off channels dorsally: the ectobronchi (Fig. i a). 



Pancreas: three rudiments, one situated behind the stomach region, the other two 

 arising as pockets from the liver diverticula. It is interesting to note that the threefold 

 origin of this gland is not always clearly indicated by three ducts in the aduh penguin. 

 Watson (1883, p. 198) records considerable variation in the number of these ducts, for 

 example in Eiidyptes. 



Maxillary ridge {mx). Mandibular ridge (m). Limb buds (e.g. h) begin to show dif- 

 ferentiation internally. 



Excretory organ: opisthonephros well established. Its ducts have acquired openings 

 into the cloaca. 



5. Stage comparable with a fowl of 8 days' incubation (Plate III, fig. i). NT 31. 

 Length 31 mm. Brain with very prominent optic lobes. Eyes socketed in epithelium, 

 through which lachrymal glands perforate later. Rudiment of nictitating membrane. 



External auditory meatus. Olfactory organs enclosed, external nares, rudiment of 

 the beak. 



Operculum {op) fully developed as a backgrowth from the hyoid arch. 



Stomach large, intestine short and scarcely coiled. Bile duct greatly distended 

 forming a gall bladder of quite exceptional size. 



Lungs growing rapidly and bearing at their hinder ends the rudiments of two of the 

 air sacs : (i) the posterior thoracic air sac, (ii) the abdominal air sac. Internally the meso- 

 bronchus of each lung has budded the rudiments of eight entobronchi on the ventral 

 side as well as the four dorsal ectobronchi. Its prolongation beyond the borders of the 

 lung forms the rudiment of the abdominal air sac, which conceals one of the entobronchi 

 beneath it in the example figured (Fig. i b). 



Limb buds (/) are marked externally by the developing digits at their tips. The dif- 

 ference in shape between the fore- and hind-limbs is becoming clearly established. 



Note. In the corresponding stage of the fowl embryo traces of feathers are apparent 

 on the rump, on the ventral body-wall, and on the hind-limbs. There are no feather 

 rudiments at this stage in penguins. 



6. Stage comparable with a fowl of about 10 days' incubation (Plate III, fig. 2). 



NT 34. 



Length 58 mm., including beak. Altogether about 20 mm. longer than the fowl at 



this stage. 



