Oldenburg he had examined this liquor three or four years before, when he took these animalcules for globules; that is, there are times when these pretended animalcules are no more than globules, without any remarkable motion, and others when they move with great activity; sometimes they have tails, and at others they have none. Speaking in general of spermatic animals he says, "Ex hisce meis observationibus cogitare coepi, quamvis antehac de animalculis in seminibus masculinis agens, scripserim, me in illis caudas non detexisse, fieri tamen posse ut illa animalcula æque caudis fuerint instructa ac nunc comperi de animalculis in gallorum gallinaceorum semine masculino;" another proof that he has often seen spermatic animals of all kinds without tails. In the second place we must remark, that the filaments which are seen in the seminal liquor before it is liquefied were discovered by Leeuwenhoek, and that in his first observations, before he had made any hypothesis on spermatic animals, he considered these filaments as veins, nerves, and arteries; and firmly believed all the parts and vessels of the human body might clearly be seen in the seminal liquor. This opinion he persisted in, in defiance of the representations which Oldenburg made to him on this subject from the Royal Society: but as soon as he thought of transforming these pretended spermatic animals into men, he no longer mentioned these vessels; and instead of looking on them as nerves, arteries, and veins, of the human body already formed in the seed; he did not even attribute to them the functions they really possess, the producing of these moving bodies: and he says, vol. I. p. 7, "Quid fiet de omnibus illis particulis seu corpusculis præter illa animalcula semini virili hominum inhærentibus? Olim & priusquam hæc scriberem, in ea sententia fui, prædictas strias vel vasa ex testiculis principium secum ducere, &c." And in another part he says, that if he had formerly written any thing on the subject of these vessels found in the seed, we must pay no attention to it. [Illustration: _PLATE. IV._]