VOL. XXIII.] PHILOSOPHICAL TRANSACTIONS. 33 



of an inch long; on a modest estimate, their thickness is not the lOOth part of 

 a hair's breadth, and consequently if you imagine a hair of your head split into 

 above 7800 equal fibres, each fibre would be as thick as one of tliese animal- 

 cules. Their motion is equable and slow, and they wave their bodies but little, 

 though sometimes they make greater undulations. They swim with the same 

 facility both backward and forward; so that I cannot distinguish at which end 

 the head is, and I have f een the same worm go forward with one end, and back 

 again wi h the other end foremost, above 20 times together. Sometimes they 

 will, like leeches, fix one end on the glass plate, on which the water is laid* 

 and move the loose part of their body round about very oddly. These I take 

 leave to call capillary eels, and they are represented at fig. c, in the several 

 postures I have seen them swim. 



I find the dust of the fungus pulverulentus, or pufF-ball,* to be the minutest 

 powder that I ever saw: to the naked eye, when crushed, it appears like a 

 smoke or vapour, and with a common microscope the particles cannot be dis- 

 tinguished: but when viewed with the greatest magnifiers, each grain is visible, 

 and exactly alike, appearing a perfect spherule, of an orange colour, something 

 transparent, whose axis is not above the 50th part of the diameter of a hair: 

 so that a cubical vessel of a hair's breadth of a side, would hold 1 25000 of them. 

 This was the dust of that fungus which is larger than one's two hands put to- 

 gether; and I observed in another pufF-ball,')- of the size of a small crab, that 

 all the globules were darker, and that every one had a little tail or stalk affixed 

 to it. 



I have met with great variety of very beautiful minute flies and insects on 

 leaves and flowers, (for at this time of the year every thing is full of animals) 

 especially one very pretty grub, which I found plentifully adhering to nettle- 

 leaves: it is a wonderful thin animal, has a sort of a covering all over its back 

 like a broad shield, which it lies under like a tortoise, and is all over beset and 

 fringed round with spikes. 



A buck from accident was killed the latter end of September, which being 

 rutting time, I thought I might with the greatest advantage observe the semen 

 masculum. Accordingly I took out one of the testicles, with the adjoining 

 seminal vessels, and found the vasa deferentia very turgid, and full of a milky 

 fluid. After various methods of viewing this liquor, I saw the animalcula in 

 vast numbers, very perfectly in several postures, moving very briskly. The 

 greatest task was to lay them thin enough before the microscope; for when the 

 matter is too thick, nothing is seen distinctly, only a confused motion ; and 



* Lycoftrdon Bovista. f Lycoperdon pruniforme. 



VOL. V. F 



