404 THE MICROSCOPE. 



partook of the blessing, like the ignorant among man- 

 kind, have their own contracted round of unenlightened 

 joys, perform their mechanical duties, and expire hidden 

 and unknown. 



On examining the structure of infusorial animalcules, 

 some are found to have a soft yielding skin, so elastic as 

 to stretch when food or other circumstances render it 

 necessary, returning again to its previous condition as the 

 cause of distension ceases ; these are designated illoricated, 

 which signifies shell-less. Others are termed loricated, 

 from being covered with a shell, which is beautifully 

 transparent, and flexible like horn. When the delicate 

 and soft substance in which the functions of life perform 

 their allotted duties perishes, the coat that protected it 

 from injury during its hours of existence remains as a 

 token of the past labours of nature ; this covering con- 

 sists mostly of siliceous material or of lime united with 

 oxide of iron, destructible in some instances either by 

 chemical agents or by fire. 



Some of these minute beings have apportioned to them 

 setce, or bristles ; these stiff hairs, attached to the surface 

 of their bodies, do not rotate, but are movable, and appear 

 to be a means for the support of their bodies, as aids in 

 climbing over obstacles that present themselves, or as 

 feelers. Others are possessed of unci, or hooks, projecting 

 from the under part of the body, which are capable of 

 motion ; and by their means the animalcule can attach 

 itself to anything that lies in its way. Some, again, 

 have styles, which are a kind of thick bristle, jointed 

 at the base, possessing a movement, but not rotary ; they 

 are in the shape of a cone, large at their base, and delicate at 

 their summit. Many, also, can extend and withdraw their 

 bodies at pleasure, in a similar manner to the snail or 

 leech. 



One of the most interesting and important organs pos- 

 sessed by infusorial animalcules is scientifically known by 

 the term cilium, which is the Latin word for eyelash, the 

 plural being cilia. Its appearance is that of a minute 

 delicate hair. 



The cilium is not only useful in the act of progression, 

 but also as an assistance in procuring food ; the twodutie* 



