88 GENERAL HI8T0ET OF 



and Stephanoceros ; in the grouping in gelatinous masses of the indi- 

 viduals of Ophrydium as compared with that of Conochilus. Again, 

 in the tubular sheath of Melicerta, with its adherent foreign matter, 

 a resemblance to some Annelida is manifested ; in the homy partially 

 investing lorica of Noteus, Brachionus, and other Rotatoria, a like- 

 ness to the Entomostraca is to be found ; and, as pointed out already, 

 the long-ciliated arms of Stephanoceros find their analogy among the 

 Cihohrachiate Polypes. 



In the classification of the Rotatoria, Ehrenberg was chiefly 

 guided by the character of the rotary apparatus — according as it 

 formed a continuous circle or wheel, when he termed it MonotrocJia, 

 or was divided into two or more segments, which he named it Soro- 

 trocJia. Proceeding on the same plan, he subdivided each of these 

 primary divisions into two sections ; the first, into HolotrocJia and 

 Schizotrocha ; the second, into PolytrocJia and Zygotroclia. (See 

 Part III., class Rotatoria.) 



Siebold and others adopt this arrangement, but, at the same time, 

 declare it defective and artificial. Mr. Gosse has employed it as the 

 most convenient yet published, but, as we are glad to see, promises 

 an arrangement more according to the organization and the natural 

 affinities of its members." (Ann. Nat. Hist. v. viii. p. 197.) 



In the further distribution into families, Ehrenberg has recourse 

 to the character of the surface, whether this be loricated, or illori- 

 cated. But the use of these terms, after this manner, in the case of 

 the Rotatoria, \& objectionable; for, as M. Dujardin remarks, "all 

 the Rotatoria are clothed by a resistant integument," and hence 

 " Ehrenberg is compelled, sometimes, to call a thicker and harder 

 portion of the common integument, the lorica ; at other times, to 

 apply the word to a diaphanous tube, or to the mucilaginous secre- 

 tion enveloping in part the Lacinularia, or to the sheath of Melicerta, 

 which is evidently a secretion with agglutinated foreign particles." 



In the construction of genera, Ehrenberg has been guided chiefly 

 by the variations in the number and disposition of the eyes. To 

 this, Dujardin also objects, for, says he, " since the eyes may dis- 

 appear, from circumstances of age, or of development, the employment 

 of this character, will place in different genera Rotatoria, which ai'e 

 but varieties of the same species." 



