INTEODUCTORY COLLECTIOIsT. 
23 
to the least instructed visitor that the so-called fin or flipper of 
the whale is composed of all the same parts — shoulder, elbow, 
wrist, and fingers — as his own arm and hand. The hind limbs 
are entirely absent ; but two bones are seen suspended at some 
distance from the spinal column, which represent the pelvic or 
hip bones of other animals. In some species of whales there 
are even traces of the thigh, knee-joint, and leg attached to this, 
and like it deeply buried within the body of the animal. 
The cases placed on the floor of the hall around the skeleton 
of the whale illustrate general laws or points of interest in 
isTatural History which do not come appropriately within the 
systematic collections of the departmental series. 
One group, in a case near the entrance to the hall, shoAvs Group iiius- 
the great variation to which a species may become subject variaUon 
under the influence of domestication, as illustrated by choice under Domes- 
examples of the best marked breeds of Pigeons, all of which 
have been derived by careful selection from the wild Eock 
Dove {Columha livia), specimens of which are shown at the top 
of the case. 
A case placed on the left of this illustrates a remarkable (jroup of Ruffs 
instance of external variation in the two sexes and at different Reeves, 
seasons, not under the influence of domestication. The birds in externai^vari- 
it all belong to one species, the Euff (Machetes pugnax), of which f^^^to^sex^and 
the female is called Eeeve, belonging to the Snipe family season.^^^ 
(Scolopacidce). In the upper division of the case are shown the 
eggs, newly-hatched young, young males and females in the first 
autumn plumage, and old males and females in winter, when 
both sexes are exactly alike in colour, size only distinguishing 
them. The large group occupying the lower part of the case, 
consists of adult birds in the plumage they assume in the breed- 
ing time (May and June). In the female the only alteration 
from the winter state is a darker and richer coloration, but in 
the males there is a special growth of elongated feathers about 
the head and neck, constituting the " ruff," from which the bird 
derives its name. In addition to this peculiarity, another may 
be observed, which is rare among animals in a wild state (though 
so common among domesticated races), that of striking diversity 
of colour in difl'erent individuals. As many as twenty-three 
specimens are shown in the case, no two being entirely alike. 
