22 EDWARD A. WILSON. 
open cracks were always to be found. During blizzards and heavy weather these cracks 
get completely hidden up in snowdrift, and one may see that the seals experience a 
certain amount of difficulty in finding them again, if they happen to have been lying 
out while the storm proceeded. In this case one finds them burrowing into the snow 
with their noses, and when they discover the crack, in all probability by this time half 
frozen up and filled with snowdrift, they commence with their teeth to work a hole 
which shall be big enough to let them through. 
Their method of enlarging a crack to make a hole has been more than once 
observed by members of our expedition in McMurdo Sound, and the evidence is 
well supported by the condition of the teeth in a really old Weddell’s Seal; this is 
well exemplified in the sample figured, where the canines and incisors are worn to 
rounded stumps (Seals, Pl. III.). The seal, fixing the canines and incisors of his 
lower jaw in the solid ice, begins to revolve the upper jaw about them, in this way 
using the teeth of the lower jaw as the fixed point of a centre-bit while those of the 
upper act as the cutting edge. This has not, to my knowledge, been previously 
observed, and it explains not only the very worn condition of the teeth, but also how 
new seal-holes rapidly appear in a narrow, fresh-formed crack in solid sea ice, even 
within a few hours, sometimes, of its opening. The seal has been known to work in 
the same way from below, and in this case one cannot but think that there must be 
sufficient air-space below the ice for breathing. 
Further examples of the wearing down of the incisors and canines may be seen in 
Skulls Nos. 47, 48, 78, and 82 of the ‘ Discovery’ Collection. 
To return to the subject of progression, it is obvious that this power of making 
holes in the ice for entrance to or exit from the water has almost entirely done away 
with the necessity for any but the most perfunctory methods of progression on 
ice and land. The hind flippers certainly are never used at all except when the seal 
is in the water, and there is no tendency whatever under any conditions to attempt 
to bring them forward in progression. That there is still free and varied movement 
in every joint of the hind limb is, however, obvious from the fantastic positions that 
it assumes when the animal, as he so often does, stretches himself, or when he ‘brings 
an irritable hind limb forward to be slowly and deliberately scratched by the long nails 
of the fore limb. The quaint attitudes thus exhibited are exemplified in several of the 
accompanying illustrations. 
It is interesting to note in this connection, too, that although when lying on the 
ice these seals are often in a very irritable condition as regards their skin, a repeated 
and careful search failed to reveal any external parasites at all. It would appear that 
the animal is quite free from anything of the kind, and one is led to conjecture that 
the constant irritation as the animals lie sleeping in the sun, is due'to the effect of 
evaporation on the salt water in their hair. It may be that the crystallisation of the 
salt, and the peculiar effect which drying has upon the hair itself, may cause the 
irritation, for the hair, instead of lying flat against the skin as it does when wet, takes 
