152 ORGANISMS ILLUSTRATING BIOLOGICAL PRINCIPLES 



these little horns was flat, their body else being roundish, save only that it 

 ran somewhat to a point at the hind end ; at which pointed end it had a 

 tail, near four times as long as the whole body, and looking as thick, when 

 viewed through my microscope, as a spider's web. At the end of this tail 

 there was a pellet, of the bigness of one of the globules of the body ; and 

 this tail I could not perceive to be used by them for their movements in 

 very clear water. . . . 



"I also discovered a second sort of animalcules, whose figure was an oval ; 

 and I imagined that their head was placed at the pointed end. These were 

 a little bit bigger than the animalcules first mentioned. Their belly is flat, 

 provided with divers incredibly thin little feet, or little legs, which were 

 moved very nimbly, and which I was able to discover only after sundry 

 great efforts, and wherewith they brought off incredibly quick motions. 

 The upper part of their body was round, and furnished inside with 8, 10, or 

 12 globules : otherwise these animalcules were very clear. These little ani- 

 mals would change their body into a perfect round, but mostly when they 

 came to lie high and dry. Their body was also very yielding : for if they so 

 much as brushed against a tiny filament, their body bent in, which bend also 

 presently sprang out again ; just as if you stuck your finger into a bladder 

 full of water, and then, on removing the finger, the inpitting went away." 



His description of the cause of movement in his little creatures is 

 amusing, yet it shows that he saw cilia plainly and estimated their 

 size quite clearly. 



"But many of the things we imagine, and the natural objects that we 

 inquire into, are very insignificant; and especially so, when we see those 

 little living animals whose paws we can distinguish, and estimate that they 

 are more than ten thousand times thinner than a hair of our beard ; but I 

 see, besides these, other living animalcules which are yet more than ten 

 thousand times than a hair of our beard ; but I see, besides, these other 

 living animalcules which are yet more than a hundred times less, and on 

 which I can make out no paws, though from their structure and the motion 

 of their body I am persuaded that they too are furnished with paws withal : 

 and if their paws be proportioned to their body, like those of the bigger 

 creatures, upon which I can see the paws, then, taking their measure at but 

 a hundred times less, it follows that a million of their paws together make 

 up but the thickness of a hair of my beard ; while these paws, besides their 

 organs for motion, must also be furnished with vessels whereby nourishment 

 must pass through them." ' 



Van Leeuwenhoek was made a member of the Royal Society for his 

 clear reports of what he saw and at his death he had sent the Society a 



1 Dobell, C, Antony van Leeuwenhoek and his "Little Animah," pp. 118 and 180, Harcourt, 

 Brace and Co. By permission of the publishers. 



