AltdoiT, believed that the whole air was filled with little 

 men and animals, countless numbers 6f which are inhaled 

 and respired with every breath. Another eminent observer, 

 Hartsoeker, maintained that the infusoria were the larvae of 

 invisible winged insects that filled the air, and he also 

 imagined that the human race was developed from a single 

 spermatozoon. It was the opinion of distinguished physi- 

 cians in France, Italy and England, that the plague was 

 produced by microscopic animalcules; and that the pesti- 

 lence v/hicli raged in Marseilles in 1720, was to be ascribed 

 to mite formed animalcules with crooked beaks and claws. 

 Opinions of this kind long prevailed, but at last their 

 absurdity subjected them to ridicule and contempt, till ihey 

 ceased to be the occasion of visionary theories. " Rash 

 conclusions," says Ehrenberg, " frivolous disputes, osten- 

 tatious speculations of philosophical heads so called, imper- 

 fect instruments, and awkwardness and hurry in the use of 

 such instruments as for that time were good, and more 

 especially preconceived notions, were then, as now, for a 

 long time a hindrance to the correct general application of 

 the knowledge which had been collected and confirmed; and 

 Leeuwenhoek continued, not less than forty years, to be 

 considered as the only especially good observer."* 



In the year 1746, Linnaus first communicated his views 

 of the spermatozoa and infusoria. He considered them as 

 lifeless, oily particles, and their movements as altogether 

 passive. This opinion he afterwards abandoned, and 

 assigned to a few of them a place among the polypi, mol- 

 lusks, and lithophytes; but by far the greater number, he 

 places in his last class, which, not inappropriately, he calls 

 " Chaos," for in this class he brings together the eels of 

 paste and vinegar, which he believed revived upon the 

 application of moisture, after having been dried for years ; 



*Infusionsthierscheu Vorredo, S. 8. 



