MANUAL OF THE INFUSORIA. 



CHAPTER I. 



INTRODUCTORY— GENERAL HISTORY OF THE INFUSORIA FROM THE TIME 

 OF THEIR DISCOVERY BY LEEUWENHOEK IN 1675 TO THE YEAR 1880. 



Inappreciable individually to the unaided vision, the countless hosts of 

 the Infusorial world, more familiar perhaps to the popular mind under 

 the designation of animalcules, or animalcula, surround us literally on 

 every side. They abound in the full plenitude of life alike in the running 

 stream, the still and weed-grown pond, or the trackless ocean. Nay, 

 more, as demonstrated in a future page,* every dew-laden blade of 

 grass supports its multitudes, while in their semi-torpid encysted or 

 sporular state they permeate as dust the atmosphere we breathe, and 

 beyond question form a more or less considerable increment of the very 

 food we swallow. Yet again, and apparently as the inevitable corollary of 

 the last-named circumstance, they occur abundantly as parasites within the 

 viscera or vital fluids of the representatives of almost every higher organic 

 group. Essentially dependent on a liquid medium for the exhibition of 

 their vital functions, there is practically, the simple conditions of air and 

 moisture being granted, no limit to the area of their distribution, no field 

 so barren but will yield its quota of strange and varied forms to the 

 industrious explorer. For the professional biologist and the dilettante 

 investigator alike, the members of this intangible and yet omnipresent 

 group of organisms present a fascination unshared by any other section of 

 the organic world. Their very intangibility and practically inexhaustible 

 variety — each improvement and augmentation of the penetrating power of 

 the optical appliances yet employed enabling us to discover, as in the sister 

 science of astronomy, " fresh fields and pastures new " for exploration — no 

 doubt represent important factors in this power of fascination, though 

 by no means the most influential ones. With the Infusoria we encounter 

 not only the as yet known most minute, but also the most elementary and 

 simply formed productions of the Creator's handiwork, though, for all that, 

 none the less complete and excellently finished. Among the Infusoria, 



* See p. 140. 



B 



