''''"^ INFUSORIA. 



idea. But, even in the present limited state of our information, tliis de]iartment ci 

 nature is a very extensive one, and requires the studj' of a whole lifetime to obtain even 

 a moderate knowledge of all its branches.] 



The greater part of the Infusoria have a gelatinous body, and a very simple organ- 

 ization ; but some naturalists have included among them other animals, which are far 

 more complex in their organization, and which agree with them only in the smallness 

 of their size, and the habitats in which they are usually found . — these will constitute 

 our first order ; but we must retain the doubts, which are not yet cleared up, respecting 

 their organization. 



THE FIRST ORDER OF THE INFUSORIA. 



R(JTIFERA. 



These are, as we have stated, distinguished by a more complicated organization. Their body 

 is of an oval shape, and gelatinous , and we can observe that they have a mouth, a stomach, 

 an mtestine, and a vent near the foot. The Ijody usually termmates in a sort of tail, variously 

 formed ; and it has on the fore part a very singular organ, variously divided into tubes with 

 toothed edges, the teeth of ivhuli vibrate in various ways, and give the organ the appearance 

 of one or more toothed wlieels, revolving with greater or less rapidity. The apparently revolving 

 organ docs not ai)])car to convey food to the mouth ; and so it may be, ni some wav, con- 

 nected witli the funetujn of respiratujn. 



FURCULARIA, 



Or tlie Kotifcra properly so called, Lave tbe body uiiarnR-d, and the tail composed of articulated portions, 

 \\iiich enter into each other. 



Trkhocerca, have the rotatory organs a little less developed. VagiiwJes, are said to resenUjle the former, 

 inclosed in a transparent membrane ; but that is doubtful. 



Tubkolaria, form for themselves Uttle habitations of foreign substances, out of which the rotatory organs are 

 protruded, in a manner similar to the tentacula of polypi. SjancAioni/s, are distinguished by a sort of membranous 

 shield on the back. 



THE SECOND ORDER OF THE INFUSORIA. 



HOIIOGRN'F.A. 



The body of tlicsc shows no viscera, or other complex organization, ami in many there is 

 not even a vestige of a mouth. 



Tlie first tribe cotniirehcnils those which, with a gilatiiions body, more or less contractile in several 

 parts, has yet ciliae, or soiue other siin[jle external organs. 



Urcolaria, have the shape of a horn, but with cilia;. Tric/ioda. have a flat body, ciliated at one extremity. 

 Lfurrip/wra, Iiave cilia' ad round the body. Keroiin, have tlic cilia; like little jinrns. IJiaiilojia, have them 

 prolonged in a sort of threads. 



The second tribe have no external organ, except a tail. 



Ca-carea, have an oval body, with a thread-tike termination. The seminal aninialcula\ wliicb have given 

 occasion to so many Hhimsical hypotheses, belong to this genus, 



Vilirio, have the body round, like a very minute bit of thread. The " Eels in paste and in vinegar," as they are 

 called, belong to this genus. 



Bnelielis, have the body oblong, more soft, and less defined than that of Vibrio. There are various other forms. 



Proleus, are so constantly changing their .slia|ie, that no definition or description of it can be givini. 



Mniins, ;uc, I'ven nniler the microscope, mere points, which move with great rapidity, though thev ha\ e no appa- 

 re.it ore-;i)is nf nicitinn. 



Volvox, are globular bodies, revolving nn their axes, and conlainiug more minute globes, each of which also, in 

 all probabiUty, contains a numerous endjryo race. 



