6l4 PHILOSOPHICAL TBANSACTlONg. [aNNO 176g. 



ing is very specious and plausible, but too metaphysical for a natural historian. 

 Yet I cannot forbear relating one of the experiments which I tried in conse- 

 quence of his discovery, that animalcula were produced in various infusions, not- 

 withstanding the greatest heat was given to the liquor. 



On May 25, 17 66, Fahrenheit's thermometer 70 degrees, I boiled a potatoe 

 in New-river water till it was reduced to a meally consistence. I put part of it, 

 with an equal proportion of the boiling liquor, into a cylindrical glass vessel 

 that held something less than half a wine pint, and covered it close immediately 

 with a glass cover. At the same time, I sliced an unboiled potatoe, and, as near 

 as I could judge, put the same quantity into a glass vessel of the same kind, with 

 the same proportion of New-river water, not boiled, and covered it with a glass 

 cover, and placed both vessels close to each other. On May 26, 24 hours 

 afterwards, I examined a small drop of each by the first magnifier of Wilson's 

 microscope, whose focal distance is reckoned at^V^h part of an inch, and to my 

 amazement they were both full of animalcula of a linear shape, very distinguish- 

 able, moving to and fro with great celerity ; so that there appeared to be more 

 particles of animal than vegetable life in each drop. This experiment I have 

 repeatedly tried, and always found it to succeed in proportion to the heat of the 

 circumambient air, so that, even in winter, if the liquors are kept properly warm, 

 at least in 2 or 3 days the experiment will succeed. 



In Mr. Needham's experiments he calls these spermatic animals ; what I 

 have observed are infinitely smaller than real spermatic animals, and of a very 

 different shape ; the truth of which every accurate observer will soon be con- 

 vinced of, whose curiosity may lead him to compare them ; and I am persuaded 

 he will find they are no way a-kin to that surprising part of nature. And though 

 some philosophers of great reputation have agreed in sentiment with Mr. Need- 

 ham, yet I am satisfied, that whenever this subject is taken up again, and pro- 

 perly attended to, the world will be convinced they have been too hasty in their 

 conclusions. 



At present I shall pass over many other curious observations, which I have 

 made on two years experiments, in order to proceed to the explaining a hint, 

 which I received last January from Mr. De Saussure, of Geneva, when he was 

 here ; which is, that he lately found one kind of these animalia infusoria, that 

 increases by dividing across into nearly two equal parts. I had often seen this 

 appearance, in various species, a year or two ago ; but always supposed the ani- 

 mals in this dividing state to be in coition. Not hearing till after M. De 

 Saussure had left this kingdom, from what infusion he had made his observation; 



and grow out of water. I hope I have already cleared up that point, in showing the absurdity ol 

 Dr. Pallas's Corallina terrestris, Phil. Trans, vol. 57, p. 415. — Orig. 



