¹ An hypothesis of this kind may be called a daring venture on the part of reason; and there are probably few even among the most acute scientists to whose minds it has not sometimes occurred. For it cannot be said to be absurd, like the generatio aequivoca, which means the generation of an organized being from crude inorganic matter. It never ceases to be generatio univoca in the widest acceptation of the word, as it only implies the generation of something organic from something else that is also organic, although, within the class of organic beings, differing specifically from it. It would be as if we supposed that certain water animals transformed themselves by degrees into marsh animals, and from these after some generations into land animals. In the judgement of plain reason there is nothing a priori self-contradictory in this. But experience offers no example of it. On the contrary, as far as experience goes, all generation known to us is generatio homonyma. It is not merely univoca in contradistinction to generation from an unorganized substance, but it brings forth a product which in its very organization is of like kind with that which produced it, and a generatio heteronyma is not met with anywhere within the range of our experience.