POLYGASTRIA. 



universal distribution wherever water is to be 

 met with fit for their reception, it is impos- 

 sible not to be overwhelmed with the con- 

 templation of a scene so calculated to impress 

 upon us the infinitude of the works of the 

 Creator. 



Our knowledge of the class of animals under 

 consideration dates from a very recent period. 

 The earliest observers with the microscope, 

 partly from the imperfection of their instru- 

 ments, and partly from ignorance of any cha- 

 racteristic distinctions, were in the habit of 

 grouping all the creatures of microscopic 

 dimensions, which they perceived swimming in 

 the water they examined, as belonging to the 

 same category, under the name of " Infusorial 

 Animalcules," a title which consequently em- 

 braced creatures of the most dissimilar forms 

 and habits, and even widely removed from 

 each other in the scale of animal existences by 

 their internal organization and general economy ; 

 thus the Rotifera, the larvae of insects, the 

 gemmules of Polyps, and innumerable other 

 minute creatures were confounded under the 

 same denomination. It is to the researches 

 of Ehrenberg, the great historiographer of these 

 beings, that we are indebted for the breaking up 

 of this chaotic assemblage, and the introduction 

 of order where all was previously confusion and 

 uncertainty. 



Prior to his discoveries naturalists denied 

 the existence of any alimentary apparatus in 

 the Infusoria, believing them to be nourished 

 by a kind of imbibition, and regarding the 

 granular bodies contained within them as being 

 their eggs or young ones. Ehrenberg, however, 

 by placing indigo, carmine, sap-green, and 

 similar extremely pure coloured vegetable sub- 

 stances in the water containing them, soon 

 found that the coloured material was readily 

 admitted into the interior of the body, and 

 there disposed in such a manner as to convince 

 him that there were numerous receptacles in 

 the interior of these little beings, which he con- 

 sidered as forming their nutritive apparatus; and 

 having applied to them the name of stomachs, 

 he was induced to establish a distinct class for 

 creatures thus organised, and distinguished 

 them from all other animals by the name of 

 POLYGASTRIA.* 



These stomachs he subsequently discovered 

 to be variously arranged in different genera, 

 and was consequently induced to make these 

 variations in the construction of the alimen- 

 tary apparatus a basis on which to erect a 

 scheme for their further subdivision. This 

 kind of nutritive system of organs he found 

 presented itself under different forms ; in some 

 species the stomachal cavities communicate 

 separately with the oral orifice, so that there 

 is no intestinal tube or passage of intercom- 

 munication between them : to such he has 

 applied the term ANENTERA.-^ In all others 

 there is a wide intestinal tube in the interior of 

 the body, to the sides of which the numerous 

 alimentary vesicles or reservoirs are appended, 



* TroXuj, many ; yao-nip, a stomach. 

 t , priv. ; IvTEpov, intestine. 



terminating by an anal orifice : these have been 

 named from this circumstance ENTERODELA.* 



The Enterodelous Polygastria are again divi- 

 sible : 



1st. Into those in which the intestinal tube 

 is disposed in a circular form in the interior of 

 the body of the animalcule, winding round so 

 that the mouth and anus are contiguous. 



(CYCLOCQELA.f) 



2nd. Into those in which the intestine tra- 

 verses the body of the animalcule, passing 

 along its longitudinal axis, and presenting two 

 orifices completely distinct and opposite to each 

 other ; that which is anterior forming the mouth, 

 the posterior the anus: such are characterized 

 as ORTHOCCELA.J 



3rd. Such as have a winding or twisted 

 intestine, which never passes in a direct line 

 through the long axis of the body : these genera 

 are named CAMPYLOCOELA. 



Such a classification, founded entirely on the 

 anatomical arrangement of one set of organs, 

 Ehrenberg acknowledges would be quite con- 

 trary to the established rules of zoology, were 

 it not that the external characters of these 

 animalcules are most exactly conformable with 

 the structure of the alimentary canal ; but find- 

 ing that the Polygastria are thus resolvable into 

 very natural families, he proceeds to classify 

 them in the following manner : 1| 



Family \. MONADINID^E (Monadida). 

 Polygastric animals, without intestinal canal, 

 without external shell, body uniform, dividing 

 by simple spontaneous fissure into two, but by 

 cross divisions into four or several individuals. 



Monas. 



Uvella, (1,/g. 1.) 



Polytoma, (2, fig. 1 .) 



Microglena, (3, jig. 1.) 



Phacelomonas. 



Glenomorum. 



Doxococcus. 



Chilomonas. 



Bodo, (4, Jig. 1.) 



Family 2. CRYPTOMONADINID&. Poly- 

 gastric animals, presenting all the characters of 

 the Monadinidae, or at least deprived of the 

 characteristic features of other families, and 

 individually enveloped in a soft or slightly 

 indurated shell. 



Cryptomonas. 



Ophidomonas. 



Porocentrum. 



Lagenella, (5, fig. 1.) 



Cryptoglena. 



Trachelomonas. 



Family 3. VOLVOCIN IDJE. Polygastric ani- 

 mals, without intestinal canal, without external 



* Evrspov, intestine ; S^Xoj, manifest. 



t xwtXoj, a circle ; xoTxoc, large intestine. 



J offls'j, straight ; itoTxoj, intestine. 



xa^uwuXo?, crooked ; xoTxo?, intestine. 



|| la the following list it will be perceived we 

 have omitted altogether the numerous families of 

 Baccillariae and kindred forms, being by no means 

 satisfied as to their claims to rank as members of 

 the animal creation. They stand, indeed, very 

 dubiously between the domains of zoology and 

 botany. 



B 2 



