Valisnieri and Bourguet, whom we have quoted, discovered small worms in the seed of a rabbit, one of whose extremities was thicker than the other; they were very lively and active, struck the liquor with their tails, and twisted and turned themselves like snakes. At last (says Valisnieri) I clearly perceived them to be real animals, "e gli riconobbi, e gli giudicai senza dubitamento alcuno per veri, verissimi arciverissimi vermi[O]." This author, who was prejudiced with the system of eggs, has, nevertheless, admitted of spermatic worms, and taken them for real animals. [O] Opere dell. Cav. Valisnieri, vol. II. page 105. M. Andry having made observations on these spermatic worms of a man, pretends that they are only found in the age proper for generation; that in the younger years, and in old age, they do not exist: that in those affected with venereal disorders there are very few, and those are languishing, and for the most part dead: that in impotent persons we do not see any alive; that these worms in the semen of men have larger heads than in that of other animals, which agrees, he says, with the figure of the foetus and the child; and he adds, those people who too frequently enjoy female amours, have generally but few or none of these animalcules in their semen. Leeuwenhoeck, Andry, and many others, strenuously opposed the egg system; they had discovered in the semen of all males living animalcules; they proved that these animalcules could not be regarded merely as dwelling in this liquor, since their bulk was greater than that of the liquor itself; and that nothing like them was found either in the blood, or in the other animal liquors. They asserted, that females furnished nothing similar, nothing alive; and it was therefore evident that the fecundity attributed to them belonged, on the contrary, to males alone: and that the discovery of these spermatic animals in the semen tended more to the explanation of generation than all that had been before supposed; since, in fact, what was most difficult to conceive in generation, was the production of the living part, all the rest being only accessary operations, and therefore no doubt could remain but these little animals were destined to become men, or perfect animals of their kind. When it was opposed to the partizans of this system, that it did not seem natural to suppose that so many millions of animalcules, every one of which might become a human being, should be employed for a purpose of which one alone was to reap the advantage; when it was asked them, why this useless profusion of the shoots of human beings? they answered, that it was only consonant with the common munificence of nature: that out of many millions of seeds which plants and trees produce, but a very few succeed, and therefore we must not be surprised at the same circumstance in spermatic animals. When the infinite minuteness of the spermatic worm, compared to man, was objected to them, they answered,