The Descent of Man and Selection in Relation to Sex, Vol. I
CHAPTER IX.
SECONDARY SEXUAL CHARACTERS IN THE LOWER CLASSES OF THE ANIMAL KINGDOM.
These characters absent in the lowest classes--Brilliant colours--Mollusca--Annelids--Crustacea, secondary sexual characters strongly developed; dimorphism; colour; characters not acquired before maturity--Spiders, sexual colours of; stridulation by the males--Myriapoda 321-340