Sirenia, nakedness of.
Sirex juvencus.
Siricidae, difference of the sexes in.
Siskin, pairing with a canary.
Sitana, throat-pouch of the males of.
Size, relative, of the sexes of insects.
Skin, dark colour of, a protection against heat.
Skin, movement of the; nakedness of, in man; colour of the.
Skin and hair, correlation of colour of.
Skull, variation of, in man; cubic contents of, no absolute test of intellect; Neanderthal, capacity of the; causes of modification of the; difference of, in form and capacity, in different races of men; variability of the shape of the; differences of, in the sexes in man; artificial modification of the shape of.