me others have, a very sweet smile,
accompanied by a strangely grave and disapproving glare in his large
blue prominent eyes. It was only apparently sugar of lead; really, it
was sugar of milk--the milk of human kindness. The smile of the lost
picture called "La Gioconda" is by fanciful people regarded as
something very wonderful. It is really the clever portraiture of the
habitual "leer" of a somewhat wearied sensual woman. It had a
fascination for the great Leonardo, but no profound significance.

CHAPTER XIII

FATHERLESS FROGS

One of the most interesting discoveries of recent date in
regard to the processes which go on in that all-important
material--protoplasm--which is the physical basis of life and the
essential constituent of "cells"--those minute corpuscles of which all
living bodies are built--was made in 1910 by a French naturalist, M.
Bataillon, and has been examined and confirmed by another French
biologist, M. Henneguy. To explain this discovery, a few words as to
well-known facts are necessary. It is well known that if we isolate a
female frog at the egg-laying season and let her swim in perfectly
pure filtered water, and proceed to deposit some of her eggs in that
water, the eggs will not germinate; they remain unchanged for a time
and then decompose--become, in fact, "rotten." It is a matter of
common knowledge that it is necessary for the eggs to be "fertilised"
in order that they may start on that series of changes and growth
which we call "development," and become tadpoles and eventually young
frogs. The "fertilisation" of the frog's eggs is effected in ordinary
conditions by the presence in the water of the pond, into which the
female sheds them, of microscopic sperm-filaments (often called
spermatozoa, or simply "sperms") which are shed into the water at the
same time by the male frog.

The egg (the blackish-brown spherical body, as big as a rape-seed,
which is imbedded in a thin jelly, and is familiar to those who are
drawn by curiosity to look into the waters of wayside ponds in spring)
is a single cell or corpuscle of protoplasm distended with
dark-coloured and other granules of nutrient substance. A single sperm
(though requiring the microscope to render it visible) is also a
single cell. It is a minute oval body, with a long serpentine tail of
actively undulating protoplasm. Hundreds of thousands of these are
shed into the water at the breeding season by the male frog. One is
eno