Every one will recall that this theory, born of the laboratory, made a tremendous commotion in the outside world. Its application to the welfare and progress of humanity gave it supreme interest, and polemics unnumbered were launched in its favor and in its condemnation. Eager search was made throughout the fields of botany and zoology for new evidence pro or con. But the definitive answer came finally from the same field of exploration in which the theory had been originated--the world of the cell--and the Marine Biological Laboratory was the seat of the new series of experiments which demonstrated the untenability of the Weismannian position. Most curious experiments they were, for in effect they consisted of the making of two or more living creatures out of one, in the case of beings so highly organized as the sea-urchins, the little fishlike vertebrate, amphioxus, and even the lower orders of true fishes. Of course the division of one being to form two is perfectly familiar in the case of those lowly, single-celled creatures such as the protozoa and the bacteria, but it seems quite another matter when one thinks of cutting a fish in two and having two complete living fish remaining. Yet this is virtually what the biologists did. Let me hasten to add that the miraculous feat was not accomplished with an adult fish. On the contrary, it is found necessary to take the subject quite at the beginning of its career, when it consists of an egg-cell in the earliest stages of proliferation. Yet the principle is quite the same, for the adult organism is, after all, nothing more than an aggregation of cells resulting from repeated divisions (growth accompanying) and redivisions of that original egg-cell. Considering its potentialities, the egg-cell, seemingly, is as much entitled to be considered an individual as is the developed organism. Yet it transpires that the biologist has been able so to manipulate a developing egg-cell, after its bisection, that the two halves fall apart, and that each half (now become an independent cell) develops into a complete individual, instead of the half-individual for which it seemed destined. A strange trick, that, to play with an individual _Ego_, is it not? The traditional hydra with its reanimating heads was nothing to this scientific hydra, which, when bisected bodily, rises up calmly as two whole bodies.