VOL. XIII.] PHILOSOPHICAL TRANSACTIONS. 605 



and squeezed their hinder parts, that I might get the seed out of the vasa defe- 

 rentia; but the animalcules I then found moved but little, because the matter 

 they were in was full of salt particles, which made me judge it to be urine. I 

 then cut open the testicles, and there I found an innumerable company of ani- 

 malcules, swimming among a sort of ill-shaped particles; these continued alive 

 till the next day, though there was but a small quantity of liquor to contain 

 them. I judge the bodies of the animalcules to have been of the thickness of 

 T-gVg- part of a hair of my head; they are represented to the best of my skill in 

 fig. 12, pi. 18, where ABC is an animalcule as it lay in the watery matter, and 

 moved itself therein ; sometimes the head appeared to be thicker than at other 

 times, and often I could see the body only from A to B, by reason of the thin- 

 ness of the tail, BC; when the animal moved itself strongly, though the pro- 

 gress were but little, the motion towards the head was like that of a snake, and 

 the tail was cast into 3 or 4 bows. Fig. D is an animalcule lying dead, and 

 stretched out at length ; but in this posture I saw but few, for many that were 

 dead lay with the fore part of their body bent in, as in fig. E ; others made as 

 it were a half circle, and others had the fore part of their body bent, and moved 

 their hinder parts; these last I took to be ready to die. The number of ani- 

 malcules in all the seed was so great, that I judge there might be 10,000 of 

 them to one of the female's eggs. The same computation I formerly made of the 

 melt of a codfish; but it must not be thought that all the animals in the melt 

 of the codfish live together, but only such of them as are nearest the passage 

 they are to be cast out of, and which have more moisture about them ; the rest 

 of them being more remote in the body, and being encompassed with a thicker 

 matter, are not alive; for though some fishes, as the bream and trout, cast 

 their melt and spawn in 2 days time, yet codfishes are about a month in doing 

 it; in all which time the seed is successively ripened and perfected. So also are 

 frogs by what I have experienced, for the first animals I sought were dead, and 

 though I afterwards found live ones, yet those were dead that lay deepest in the 

 testicle. 



It is well known, that when a cock has trodden a hen but once, many eggs 

 are made fruitful ; the reason that I give for it is, that many of the eggs in the 

 ovarium have each of them received an animalcule out of the male seed. This 

 animalcule, while the egg is sat upon, does not presently take the figure of a 

 chick, but grows into a disorderly bulk, wherein the heart is first plainly to be 

 discerned. Other foetuses have a different way of growth ; the louse has all its 

 parts, and is a breeder, while it is yet in the egg : the flea shows like globules 

 swimming in a watery substance, it afterwards becomes a worm, then a nym- 

 pha: the frog is a thick worm till it be of a considerable size: the human 



VOL. II, 4 Q 



