236 MR HAROLD AXEL HAIG ON 



and the ureters are to be seen opening into the bladder laterally upon its dorsal 

 aspect ; it is noteworthy that in the seals the bladder is represented by the entire 

 intra-abdominal extent of the allantois.* 



Summary of the Anatomical Features. 



From the foregoing description it will be readily gathered that the Sea-Leopard 

 Seal, during the middle phase of foetal life, presents fairly typical embryological 

 features ; the age of the present specimen can hardly be worked out with any 

 approach to accuracy, but it may be stated that the stage of development of most 

 of the organs would place the foetus at about the end of the first third of intra- 

 uterine life. The exact period of gestation of seals is, however, somewhat difficult 

 to determine owing to the peculiar habits of mating which these animals have, so 

 that the above estimate should be accepted with some reservation. 



In summarising the main anatomical features, it is possible to pick out the 

 following more obvious characters : — 



(a) In the brain : firstly, the relatively advanced stage of the cerebellum, the 



hemispheres of this portion showing distinct evidence of folds and sulci 

 which are not to be made out in a three-months human foetus ; secondly, 

 the comparatively advanced development of the pituitary body, a feature 

 which will be more readily appreciated when the histology of the hypo- 

 physis is considered (see infra). 



(b) In the heart : the most prominent feature is the late persistence of the bulbus 



aortse, whilst the peculiar shape of the auricular appendices is also worthy 

 of note. 



(c) In the lungs : the possession of an accessory lobe by the right lung, and the 



relative size of these organs, which are certainly large, are points of com- 

 parative value. 



(d) Other points which may be emphasised are the large size of the thymus and 



the left-sided deviation of this organ, the apparent absence of a thyroid 

 isthmus, and the large size of the lowest parathyroids ; in connection with 

 the alimentary tract, the forward position of the csecal diverticulum and 

 the great length of the lobes of the liver. The kidneys are noteworthy on 

 account of their surface lobulation into numerous renal pyramids, whilst 

 the adrenal bodies do not lie directly upon the anterior poles of the kidneys. 

 Moreover, the adrenals are relatively much smaller than is. the case with 

 these bodies in the human foetus at a corresponding stage of development. 

 Lastly, certain external characters, such as the absence of an external ear and 

 the protruding bifid tip of the tongue, are features so obvious as to need 

 no further comment. 



* Hkfbukw, Trans. Roy. Soc. Edin., vol. xlviii. part i., No. 3, 1913. 



