as into its Uterus, spreads forth its Roots, and receives its Nourishment, but has its form within its self, and we may rationally conjecture some such Analogy in the Propagation of Animals.
The third Particular which later Discoveries make probable, is, that Animals cannot be formed of these Animalcula without the Ova in fœminis , which are necessary for supplying of them with proper Nutriment: And this these Considerations seem to evince. 1. It is probable that an Animalcle cannot come forward, if it do not fall into a proper Nidus . This we see is the Cicatricula in Eggs; and tho' a Million of them should fall into an Egg, none of them would come forward, but what were in the Center of the Cicatricula ; and perhaps the Nidus necessary for their formation is so proportion'd to their bulk, that it can hardly contain more than one Animalcle ; and this may be the reason why there are so few Monsters. This we see is absolutely necessary in Oviparis ; and the only difference which seems to be between them and the Vivipara , in this matter, is in this, that in the latter the Ova are properly nothing more but the Cicatricula , with its Colliquamentum , so that the Fœtus must spread forth its Roots into the Uterus to receive its nourishment; but the Eggs in Oviparis may be properly term'd an Uterus , in relation to the Fœtus ; for they contain not only the Cicatricula , with its Amnion and the Colliquamentum , which is the immediate nourishment of the Fœtus , but also the materials which are to be converted into that Colliquamentum ; so that the Fœtus spreads forth its Roots no farther than into the White and Yolk of the Egg, from whence it derives all its nourishment. Now that an Animalcle cannot come forward without some such proper Nidus , Mr. Leewenhoeck will not readily deny; for if there were nothing needful, but their being thrown into the