PRR YEOSIS "OE BERDS 
that the feathers are disposed in definite tracts, whose 
arrangement varies from bird to bird, and often affords 
valuable evidence of affinity : between these tracts are 
either naked spaces or spaces sparsely covered with scat- 
tered small feathers. The penguin, on the other hand, 
has a ** pterylosis,”’ which is continuous all over the body, 
save, as it appears, for a small region on the under 
surface, which is pressed upon the eggs when the bird 
is sitting on its nest. In this way the eggs get more of 
the heat of the body ; for, as is well known, feathers are 
bad conductors of heat, and are thus useful for keeping 
a bird warm, and us when we use feather muffs, duvets, 
etc. It is a remarkable fact that this little bare patch 
only occurs in the female, and yet both sexes sit upon 
the eggs. Perhaps it argues that the share of the 
father in the well being of his offspring is only a recent 
occurrence, and that formerly the hen alone performed 
this important function. This feathering of the pen- 
guin is supposed by some to indicate the retention of 
an archaic character. And if the feathers of a bird 
may be derived directly from the scales of some reptile 
forefather, an uniform feathering would naturally be 
the original condition. Speaking of the scales of some 
reptilian ancestor, it is a most noteworthy fact that the 
difference between a scale and a feather is reduced 
to an apparently irreducible minimum in the paddle. 
Flat, closely depressed and unbarbed ‘‘ feathers” cover 
that member, and it was discovered by the late Mr. 
A. D. Bartlett that the skin of the fore arm is shed 
in a piece, like the skin of a snake, instead of being 
moulted in bits like the feathering of a fowl. Another 
ancient character (at least in the opinion of some), 
which the penguin shows is the fact that the three 
bones in the foot known as the metatarsals, those 
bones which lie between the ankle and the commence- 
ment of the bones of the toes, are slightly separated 
Ten 225 Q 
¥, 
