THE SYSTEMATIC ANATOMY OF A FCETAL SEA-LEOPARD. 455 



Serial sections taken coronally through the heart show that the foramen ovale is 

 a feature at this phase, but the aperture is a very narrow one, and will not admit a 

 glass seeker of more than 1 mm. diameter. 



From the above description it will be seen that the heart of Stenorhynchus during 

 early foetal life corresponds more or less closely with the typical mammalian organ 

 in its developmental aspects ; the iuterventricular furrow, however, is a marked ex- 

 ternal feature, and during development, at least in the Weddell Seal, it becomes 

 deeper, so that the full-grown heart possesses a bifid apex, the tips of the two 

 ventricles being separated by a deep notch.* 



(iii.) The liver, stomach, and intestines (PI. III. figs. 1 and 5). In some respects 

 the liver of this specimen shows characters similar to those of the human foetal organ, 

 but the accessory lobes, and the clefts which produce these, are to a certain extent 

 atypical ; thus the right lobe shows from the ventral aspect a fissure which passes 

 obliquely inwards from the lateral surface, but this fissure is not seen from behind, 

 as it extends for only a short distance into the substance of the lobe. 



From the dorsal aspect (PI. III. fig. 5) it appears that the left lobe is the bulkier 

 of the two, and the inner surface of this lobe shows depressions corresponding to 

 the ventral surface of the stomach, a small area of the spleen, and anteriorly the 

 oesophagus and vena cava ; the inner surface of the right lobe shows dorsally de- 

 pressions corresponding to the numerous subdivisions of the right kidney, whilst the 

 lateral aspects of both lobes are grooved by five or six of the posterior ribs. In the 

 middle line ventrally the umbilical vein (PI. III. fig. 5, l.v.) forms a thick cord, 

 passing towards the ductus venosus. 



The gall-bladder is not seen from the dorsal aspect except when the lobes are 

 widely separated, when it appears as an elongated sac, deeply embedded in the deep 

 surface of the right lobe, the fundus presenting veutrally in the small opening noted 

 in the topographical description (see supra). 



Certain accessory lobes show up when the two main lobes are separated from one 

 another : these may possibly be the homologues of the Spigelian and quadrate lobes 

 of the human organ, but their relations are somewhat different. 



The main points for comparison to be noted in this organ are : 



(i.) The relative longitudinal extent of both lobes, this being distinctly greater 



than is the case with most other carnivora. 

 (ii.) The small accessory flap guarding the aperture in which, ventrally, the fundus 



of the gall-bladder is to be seen. 

 (iii.) The large volume of the abdominal cavity, occupied by the whole liver, at a 



stage when other abdominal viscera have assumed a relative importance 



in size. 



The stomach and intestines (PI. III. fig. l) are seen from the ventral aspect, after 



* See HEPBURN, Trans. Roy. Soc. Edin., vol. xlviii., 1913. 

 (ROY. soc. EDIN. TRANS., VOL. L., 233.) 



