10 GENERAL CONSIDERATIONS 



living creatures in rain water whicli had stood but four days in a new 

 earthen pot, glased blew within. This invited me [he continues] to view 

 this water with great attention, especially those little animals appearing to 

 me ten thousand times less than those represented by Mons. Schwammerdam 

 and by him called Water fleas or W^ater-llce, which may be perceived in the 

 water with the naked-eye. The first sort by me discover'd in the said water, 

 I divers times observed to consist of 5, 6, 7, or 8 clear globuls, without 

 being able to discern any film that held them together, or contained them. 

 When these animalada or living atoms did move, they put forth two little 

 horns, continually moving themselves. The place between these horns was 

 flat, though the rest of the body was roundish, sharp'ning a little towards 

 the end, where they had a tayl, near four times the length of the whole 

 body, of the thickness (by my microscope) of a spiders-web; at the end of 

 which a globul, of the bigness of one of those which made up the body; 

 which tayl I could not perceive, even in very clear water, to be mov'd by 

 them. These little creatures, if they chanced to light upon the least filament 

 or string, or other such particle, of which there are many in water, especially 

 if it hath stood some days, they stook entangled therein, extending their 

 body in a long round, and striving to dis-intangle their tayls whereby it 

 came to pass, that their whole body lept back towards the globul of the 

 tayl, which then rolled together Serpent-like, or after the manner of copper 

 or iron-wire that having been wound about a stick, and unwound again, 

 retains those windings or turnings. This motion of extension and contraction 

 continued awhile; and I have seen hundreds of these poor little creatures, 

 within the space of a grain of gross sand, lye cluster'd in a few filaments. 

 (From Calkins, 1901, p. 5.) 



This is the first description of a protozoon; and though the descrip- 

 tion is incomplete, it undoubtedly refers to a species of Vortkella. Leeu- 

 wenhoek observed several other forms, but their identity is uncertain. 



Leeuwenhoek allowed his imagination to see what his eyes could not. 



When we see [said he} the spermatic animalcula [spermatozoa} moving by 

 vibrations of their tayls, we naturally conclude that these tayls are provided 

 with tendons, muscles, and articulations, no less than the tayls of a dormouse 

 or rat, and no one will doubt that these other animalcula which swim in 

 stagnant water [Protozoa} and which are no longer than the tayls of the 

 spermatic animalcula, are provided with organs similar to those of the 

 highest animals. How marvellous must be the visceral apparatus shut up 

 in such animalcula! (Quoted from Dujardin, 1841, pp. 21-22.) 



In a letter a year later Leeuwenhoek further says: "The fourth sort 

 of little animals . . . were incredibly small; nay, so small, in my sight 

 that I judged that even if one hundred of these very wee animals lay 



