200 GEA'EEAL HISTORY OF THE INFUSORIA. 



of the collection of li^-ing objects assembled in that class ; and even Ehrenberg 

 himself would never have suggested such a grouping, had he not imbibed the 

 hypothesis of a pervading uniformity of organization possessed by the simplest 

 animated beings in common mth animals considerably advanced in the scale, 

 and under its influence, aided by his imagination, found in all these various 

 organisms, a polygastric structure, viz. an apparatus of numerous stomach- 

 sacs, communicating dii^ectly or indirectly with the mouth. Notwithstanding 

 the many prominent errors in Ehrenberg's classification, he rightly recognized 

 in framing it the value of the external means of locomotion, and distinguished 

 a group of PoJygastrica under the name of Pseudopoda. 



Siebold, who proposed the term Protozoa, limited it to two classes, distin- 

 guished as the ' Infusoria ' and the ' Rhizopoda ', omitting the supplementary 

 groups above mentioned. The Infusoria he di\ided into two orders, the 

 * Astoma ' and ' Stomatoda,' the latter of which, together with two of the 

 three families of Astoma, is e(]uivalent to our class Ciliata, its remaining 

 family Astasuea being a member of oiu' group of Phytozoa. 



The Protozoa, as understood by us, may be thus exhibited at one view. 



Ciliata. Eiiizopoda. 



f. . r Opalingea a. Amoebsea 



a. s oma | Peridinigea (?) b. Monothalamia or Monosomatia 



b. Stomatoda 



c. Polythalamia, Polysomatia, or 

 Foraminiiera. 



Gregarinida 

 Psorospermia 



N^JUill Suppleruentar, groups. 



' Polycystina 

 ThalassicoUida 

 Spongiada 



In treating of these several classes and groups we shall commence with 

 the Phkopoda, omitting, however, lest our subject-matter be too much ex- 

 tended, the Polycystina, ThalassicoUida, and Sjjongiada ; we shall next pro- 

 ceed with a brief description of the Greyarinida, and its subordinate family 

 Psorospermia, and then after considering the Opalinoea and Peridinicea as 

 intermediate groups, proceed to detail the history of the perfect Ciliata — 

 the Stomatoda, — finishing our account Avith the Ichthydina and Noctilucida 

 as the highest developments of Protozoic life. 



As a result of our inquiry, we shall see, on the one hand, in the true 

 Ciliata, sim^^le animal organized matter, with a very sKght amount of differ- 

 entiation, attain its acme of development in the Vorticellina, and in these 

 animalcules exhibit a superiority in organization above the lowest links of 

 groups relatively higher in the chain of animal life ; and, on the other hand, 

 in the Rhizopoda, of still simpler organization, the same organic living 

 material developed in a totally different dii'ection to a maximum in the most 

 beautiful and complex- shelled Foraminifera, which in outward form, although 

 in no real homology, emulate the highest class of Invertebrata, viz. the 

 Cephalopoda 



Another lesson may also be derived from the objects of our present study, 

 viz. the fact of the marvellous variations which can be made out of one or, it 

 may be, two elementary stnictm^es. Thus the simple contractile substance which 

 can live independently in the Amoeba condition (XXI. 1-4 ; XXII. 1-23) 

 encases itself in a one-chambered shell in the Monothalamia (XXI. 6-19), 

 and into a many- chambered one in the Polythalamia (XXI. 20-36), and again 

 lives partly within and partly without the curious silicious skeleton of Poly- 



