hibians, reptiles, birds, and mammals. The chief point of novelty
in M. Bataillon's discovery is that we have now an experimental
demonstration of parthenogenesis in a vertebrate animal, and in one so
highly organised as the frog. And equally interesting, indeed more
important from the point of view as to the real meaning and nature of
fertilisation, is the mode in which the parthenogenesis of the frog is
set going, namely, by a mere prick of the surface film of the ripe
egg!

There have, however, been important experiments on the subject of the
development of eggs without fertilisation in recent years, prior to
these discoveries as to the frog's egg. A favourite subject for such
inquiries is the sea urchin (Echinus of different kinds). The female
sea urchin, or sea egg, like its close allies the star fishes, lays a
great number of very transparent minute eggs (each about the 1/200th
of an inch in diameter) in sea-water, and they are there fertilised by
the mobile sperm filaments discharged by the males. The eggs are so
transparent and so easily kept alive in jars of sea-water that there
is no difficulty in watching under the microscope the penetration of
the egg by a sperm, and the fusion and other changes in the nuclei.
Delages of Paris, and Loeb of California, have made valuable studies
on these eggs. Loeb has shown that they may be artificially
started on the course of development and cell division without
fertilisation--simply by the action of minute quantities of simple
chemicals (fatty acids, etc.) introduced into the sea-water by the
experimenter. These chemicals appear to act on the delicate pellicle
which forms the surface of the egg-cell in much the same way as the
prick of a needle acts on a frog's egg. A limited and delicately
adjusted disturbance of the cohesion (or of the surface-tension) of
the egg-cell seems to be all that is necessary for starting the
egg-cell on its career of development. It becomes, in the light of
these experiments, not so much a wonder that egg-cells should develop
"on their own," but that they do not more frequently do so. It must be
remembered that the "germination" and development of unfertilised
eggs, even when the whole range of animals and plants is taken into
account (for plants also are reproduced by single cells identical in
character with the egg-cells and sperm-cells of animals), that is to
say, the existence of "parthenogenesis" as a natural, regularly
recurring proces