The Indirect Action of Changed Conditions

Many facts clearly show how eminently susceptible the reproductive system is to very slight changes in the surrounding conditions. How many animals there are which will not breed though captain almost free state in their native country? This is generally, but erroneously, attributed to vitiated instincts. Nothing is more easy than to tame an animal, and few things more difficult than to get it to breed freely under confinement,. even when the male and female unite. The variability that follows from crossing of distinct species may be served with plants and animals when reared under new or unnatural conditions.