392 Proceedings of the Royal Physical Society. 
legists of his time, and of Blumenbach and Houston in more 
modern 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 j9ro 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 difi'ered 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" 
])y the sealers. This colour gradually changes into a dark- 
