XI. Having procured the seed of a dog, emitted naturally, I observed that this liquor was clear, and had but little tenacity. I put it in a phial, and having examined it with a microscope, without diluting it with water, I perceived moving bodies entirely like those I had observed in the human semen; they had threads, or tails, perfectly the same; they were also nearly of the same size; in a word, they resembled, as perfectly as possible, those I saw in the human liquor, liquified during two or three hours. I then sought for the filaments which I had seen in the human liquor, but it was useless; I perceived only some long threads entirely like those which served as tails to the globules. These threads were not attached to any globules, nor had they any motion. Those globules which were in motion, and had tails, appeared to me to move quicker than those in the human semen: they had scarcely any horizontal vibrations, but a rolling motion. They were not in a great number; and, although their progressive motion was stronger, they took more time to cross the microscope than those I had before remarked. I observed this liquor for three hours, but perceived no change: after which I examined it at another time for four hours, and remarked, that the number of moving bodies diminished by degrees; the fourth day there was still some, though they were very few, and often I only found one or two in a drop of liquor. The second day most of them were deprived of their tails; the third day very few retained them, yet, at the last day, there still remained some which had them; the liquor had then deposited a whitish sediment, which appeared to be composed of immoveable globules, and many threads, that seemed to be tails separated from the globules. There were also some attached to the globules, which appeared to be the dead bodies of these little animals, but whose forms were different from those that moved, for they appeared larger than the moving globules, or the rest, which remained without motion at the bottom of the liquor, and appeared to have a fissure or opening.