The particular difficulties that may be raised against this egg system are no less considerable. If the foetus exists in the egg before the communication of the male with the female, why do we not perceive the foetus as well in those eggs produced before as after copulation? We have before recounted the observations of Malpighius, who says he always found the foetus in those eggs produced by hens that had received the cock, and only a mass or mole in the cicatrice of those who had not; it is therefore very clear that the foetus does not exist in the egg till after impregnation. Another difficulty against this system is, that not only the foetus is not seen in eggs before the junction of the sexes, but even the existence of eggs in viviparous animals is by no means proved. Those physicians who pretend that the spermatic worm is the foetus enveloped in a covering, are at least assured of spermatic worms; but those who affirm that the foetus is pre-existing in the egg, have no proof of the existence of the egg itself; on the contrary, there is a probability, almost equivalent to a certainty, that these eggs do not exist. Although the partizans of the egg system do not agree what must be looked on as the true egg in the female testicle, nevertheless they all think that impregnation is made in the testicle called the _ovarium_, without paying any attention that if it was so most foetuses would be found in the abdomen instead of the matrix, for the superior extremity of the trunk being separated from the ovarium, the pretended eggs must often fall into the abdomen. Now, it is certain that this case is extremely rare, and, I believe, never happened, unless occasioned by some accident. The general difficulties and objections against these two systems have been noticed by the author of _Venus Physique_, whose treatise, although very short, has more philosophical ideas than there are in many folio volumes on generation. As this book is very public, and the accuracy with which it is written will not permit any extract, I shall only observe, this author is the first who has returned into the road of truth, from which we were farther strayed than ever, since the supposition of the egg system, and the discovery of spermatic animals. Nothing therefore remains farther to be said, and I shall conclude with relating a few particular experiments, some of which have appeared favourable, and others contrary, to these systems.