ON DYSTERIA 475 



The occurrence of transverse fission was noticed very distinctly in 

 one case ; but it is remarkable that, notwithstanding the great number 

 of specimens which were observed, no other instance of this mode of 

 multiplication came under the notice of Mr. Dyster or myself It 

 would appear that the " apparatus ' disappears, and is reproduced 

 during fission, for in the single case observed, mere rudiments of 

 it were to be seen in each half of the strongly constricted mass. 



Dysteria has not hitherto been observed to become encysted, 

 although this condition has been carefully sought for. 



There can, I imagine, be little doubt as to the true systematic 

 position of Dysteria. The absence, in an animal which takes solid 

 nutriment, of an alimentary canal with distinct walls, united with 

 the presence of a contractile vesicle, with the power of transverse 

 fission, and with cilia as locomotive organs, is a combination of 

 characters found only in the Infusoria. In this class, again, the 

 existence of a sort of shell or lorica, constituted by the structureless 

 outer layer of the body ; the presence of a submarginal ciliated groove 

 around a large part of the margins of the body ; and the inequality 

 of the two lateral halves, leave no alternative save that of arranging 

 Dysteria near or in the Eitplota of Ehrenberg. 



Indeed there is one species figured by Ehrenberg (' Infusions- 

 thierchen,' p. 480, pi. 42, fig. xiv.), Euplotes macrostylus, found 

 at Wismar, on the Baltic, which, in general aspect, and in the 

 possession of a foot-like appendage, so closely resembles the present 

 form, that were it not for the absence of any allusion to the amethy- 

 stine globule, or to the " apparatus,'' I should be strongly inclined to 

 think it identical with Dysteria. That an internal armature is not 

 inconsistent with the general plan of the Euplota, is shown by Chlami- 

 dodon, whose apparatus of styles would probably repay re-examination. 



Notwithstanding certain analogies which might be shown to exist 

 between the manducatory apparatus of some Rotifera (see e.g., that of 

 Fiircularia marina, figured by Mr. Gosse, in his excellent memoir, 

 'Phil. Trans.,' 1846) and the "apparatus" of Dysteria, I see no 

 grounds for regarding the latter as in any way an annectant form 

 between these groups. 



DESCRIPTION OF PLATE VII. (XXX.] 



Fig. 13. Dysteria arniaia. 

 Fig. 14. Part of mouth of ditto. 

 Fig. 15. Process between two styles. 



