Pearls and Parasites

Most of the following essays have appeared in the pages of the Quarterly Review, and I am greatly indebted to the editor and to the proprietor of that periodical for permission to reprint them. The article on ''The Infinite Torment of Flies'' is an address I delivered before the British Association at Pretoria in 1905, and the eighth essay appeared in Science Progress.As far as possible I have tri...