Reproduction in the simplest living things takes place by a simple division of the body into two as soon as its maximum size or adult condition has been attained. In such simple types the body consists only of a single “blob,” or particle, of jelly. But a new era began when large numbers of such particles, or “cells,” began to form coherent masses, different parts of the mass performing different work for the mutual benefit of the community. Some have come to form what we call the body, which is born, and in due course dies. Others are alone concerned with the task of reproduction. They are nourished by the body, and on attaining maturity, give rise to new bodies. These reproductive cells are excessively small. The male, or “sperm” cell, can only be distinguished under the highest powers of the microscope. The female cell, or “Ovum,” is always larger than the male, because, in addition to the germinal matter which it contains, it is furnished with a store of food in the shape of yolk. This accounts for the relatively enormous size of the egg of the hen. Within the hardened shell the germ develops into the chick, deriving food for its growth from this generous store. Where this yolk is limited in quantity the growing body is hastily fashioned, and launched forth into the world in the form of a “larva,” when it must forage for itself till it has attained its adult form. Or it is retained within the body of the mother until development is complete. The reproductive cells are the bearers of the Germ-plasm, the stuff of which man and the beasts of the field alike are fashioned. Only a portion of this germ-plasm gives rise to a new body; the rest is, as it were, held over and stored within the new body to give rise to another in due course. That which produces the body we call the “Somatoplasm,” because it is the “plasm” or stuff of which the “Soma,” or body, is made. As to the nature of this Germ-plasm and its mysterious properties, a wide divergency of opinion exists among _savants_. But the views which find most favour to-day are those of the veteran Professor August Weissmann, as set forth in his work on the “Germ-Plasm, a Theory of Heredity.” The excessively minute quantity of this germ-plasm which suffices to form a new body is incredible. By what miracle of miracles is the essence of a man distilled? His body arises from the union or commingling of two particles of living matter so minute as to be invisible to the naked eye. One of these particles is the “sperm”—cell furnished by the male parent; the other, the “ovum,” furnished by the mother. True the ovum may measure as much as the one-hundred and fiftieth part of an inch, but the bulk of this is yolk-food necessary to furnish the tender germ with life and energy till it shall have attached itself to the walls of the womb, whence all its future nourishment is derived.