Leeuwenhoek, who imagined all these moving bodies were animals, and established a system thereon; who also pretended, that spermatic animals must become men and animals, now suspected they were only natural machines, or organic particles in motion; for he does not doubt these spermatic animals contained the great animal in miniature, he says, "Progeneratio animalis ex animalculo in seminibus masculinis omni exceptione major est; nam etiamsi in animalculo ex semine masculo unde ortum est, figuram animalis conspicere nequeamus, attamen satis superque certi esse possumus figuram animalis ex qua animal ortum est, in animalculo quod in semine masculo reperitur, conclusam jacere sive esse; & quanquam mihi sæpius conspectis animalculis in semine masculo animalis, imaginatus fuerim me posse dicere, en ibi caput, en ibi humeros, en ibi femora; attamen eum ne minima quidem certitudine de iis judicium ferre potuerim, hujusque certi quid statuere supersedeo, donec tale animal, cujus semina mascula tam magna erunt, ut in iis figuram creaturæ ex qua provenit, agnoscere queam, invenire secunda nobis concedat fortuna." This fortunate chance, which Leeuwenhoek desires, presented itself to Mr. Needham. Every part of the spermatic animals of the calmar are easy to be seen without a microscope; but they are not young calmars, as Leeuwenhoek thinks, nor even animated, although they are in motion, but only machines which must be regarded as the first produce of the union of organic particles. Although Leeuwenhoek had not such an opportunity of undeceiving himself, he nevertheless had another phenomena which ought to have had that effect; for example, he had remarked that the spermatic animals of a dog often change their figures, especially when the liquor was on the point of evaporating; that these pretended animals had a hole in the head when they were dead, and that this hole did not appear when they were alive; he had seen that the part which he looked upon as the head was full and plump when it was alive, and flaccid and flat when dead. All this ought to have led him to doubt whether these moving bodies were real animals; and consider it as agreeing better with a machine, which empties itself like that of the calmar, than with a moving animal.