18 MARINE MAMMALS OF THE NORTH-WESTERN COAST. 
or squid upon which they prey. The group of Dolphins is made up of those com- 
prised in the Linncean genus Delphinus, and others, whose heads preserve the usual 
proportion to the body, and whose upper and lower jaws are set with sharp and 
usually conical teeth. They are the most active and rapacious of the whole order 
of Cetaceans. 
All Cetaceans produce their young in nearly the same manner as other mam- 
mals. The male is commonly called a bull ; the female a cow. The attitude of 
the two sexes when having intercourse with each other has been differently repre- 
sented by numerous observers. Some maintain that the male covers the female ; 
while others are positive of their lying on their sides breast to breast, or assuming 
a perpendicular position. From personal observation, however, we are justified in 
stating that all are correct. In fact, it may readily be seen that, with their united 
efforts, it is easy for the animals to sustain any desired position in their native 
element, during the period of coition. The time of gestation is not known ; but 
from our observations we believe it is never less than nine months, and that in 
some species it extends to one year. The offspring of the female is called her 
calf; she nourishes it with rich milk drawn from two teats which lie on each side 
of her abdomen. 
All Cetaceans are destitute of the hair or fur which protects the surface of 
other marine mammals, and instead thereof the dermis is covered by a smooth and 
transparent scarf-skin. Under the dermis is the thick layer of fat, or "blubber," 
which infolds the whole creature, whose flesh is dark and sinewy, resembling coarse 
beef. The natural term of life in Cetaceans can only be approximately determined ; 
it is probably from thirty to a hundred years. The new-born young are clothed 
in fatless blubber with a thick dermis, and over all is a delicate cuticle. The calf, 
or "cub," follows the dam for several months — perhaps a year with some species — 
and during that time draws its chief sustenance from the mother. As her charge 
matures, its blubber thickens and becomes fat, the dermis becomes thinner but more 
compact, and the cuticle strengthens and presents a lively glossiness. 
Among the Bakenidce, the baleen with its fringes grows rapidly, and hardens as 
it matures. As old age comes on, the fringes to these horny plates become de- 
cayed and broken, and in some instances the baleen falls out. The thick blubber, 
once filled with oil, becomes thin and watery, and, for want of proper sustenance, 
the animal yields to the course of Nature and dies. Among the Physeteridce, the 
teeth of the young are sharp and perfect when first developed ; but they become 
more or less broken and worn with age : as years advance, they either fall out or 
are reduced to a level with the gums, and, like the BalmnidcB, being deprived of the 
