Conditions of Existence as Affecting the Perpetuation of Living Beings

A philosophical study presented by the biologist author has been depicted in this book. There is no doubt that breeds may be made as different as species in many physiological characters. So with Dogs in their habits and instincts. It is a physiological peculiarity which leads the Greyhound to chase its prey by sight, —that enables the Beagle to track it by the scent, that impels the Terrier to its rat-hunting propensity, and that leads the Retriever to its habit of retrieving. These habits and instincts are all the results of physiological differences and peculiarities, which have been developed from a common stock, at least there is every reason to believe so.