392 Proceedings of the Royal Physical Society. 



logists of his time, and of Blumenbach. and Houston in more 

 modem times, are the most celebrated. The first is unten- 

 able, as Dr Wallace found the foramen ovale unclosed in only 

 one of the many hearts which he examined ; and in regard 

 to the venous sinuses said to have been found by the latter 

 anatomists in the liver and neighbouring parts, he had seen 

 nothing which deserved the name. The venous system on 

 the whole, and not in any particular part, unless in the vena 

 cava, from the pressure exerted on its walls, is greatly en- 

 larged, but this arises from the great quantity of blood these 

 animals possess. Moreover, supposing these sinuses to exist, 

 they could not contain the full quantity of blood that may 

 return in that period from the capillary system. Their 

 power of remaining so long below the water is to be referred 

 to a cause physiological, and not structural. 



Their expertn ess in swimming is not acquired from birth, 

 but only as an innate instinct. On first taking the water, 

 they swim about in the smooth pools among the ice, and 

 then swimming slowly and quietly about, seldom remaining 

 longer than a few minutes below the surface. This train- 

 ing, coupled with the enormous quantity of blood which they 

 contain, and their slow respiration, will account for their 

 capability of enduring pro tempore a sub-aquatic life. 



1. Phoca Grcenlandica, Mull. (The " Saddleback" of the northern 



sealers.) 



The most common length is five feet and a-half. The 

 author had noticed some which differed so much from the 

 typical specimens as to have led to the belief by the sealers 

 of their being different species. 



Lepechin's description of his Phoca oceanica is about the 

 best description of the present species extant. The colour 

 of the young at birth is a pure white, which gradually 

 assumes a beautiful yellowish tint ; they are then called 

 " white-coats," and they retain this colour until they are able 

 to take the water (when about fourteen or twenty days old) . 

 The colour of their hide changes at the same time to a dark 

 speckled and spotted hue. Such are denominated " hairs" 

 by the sealers. This colour gradually changes into a dark- 



