WHALES AND DOLPHINS. 
83 
fonh iheir yonng alive, and nourishing them tor a time with 
milk, they agree with the other members of their class ; the 
striking external differences being all in relation to their 
aiJaptation to an entirely aquatic mode of life. Their external 
form is fish-like, the body being spindle-shaped, passing into 
tlie head usually without a distinct neck, and tapering behind 
gradually towards the extremity of the tail, which is provided 
with a pair of lateral pointed expansions called flukes ; 
thus forming a horizontally-placed triangular propelling organ, 
notched in the middle line behind, with which these animals 
drive themselves through the water. 
Fig. 48. 
Sperm -}N HALE. 
WHALE GALLERY. 
LEADING OUT OF BIRD GALLERY.) 
The head is generally large, in some species attaining more 
than one- third the entire length of the animal, and the mouth is 
wide, and bounded by nearly immobile lips. The fore-limbs 
are reduced to flattened paddles, encased in skin showing no 
external sign of division into arm, fore-arm, and hand, or of 
separate toes, and without trace of nails. No traces of hind- 
limbs are visible externally. The general surface of the skin is 
smooth, glistening, and devoid of hair, although in most species 
there are a few fine bristles in the neighbourhood of the mouth, 
which either remain throughout life or are found only in the 
young state. Immediately beneath the skin is a thick layer of 
g2 
