DYSTERIA. 



171 



appearing from this point of observation more like a slit or fur- 

 row trending parallel with the side of the body. An end view 

 of the animal has a strong resemblance to the disc of the 

 trumpet-shaped Stentor (fig. 30) ; much more even than a sim- 

 ilar view of Paramecium (fig. 97). 



The extreme of obliquity in this type 

 is best exemplified in a minute marine In- 

 fusorian which is called Dysteria (fig. 100). 

 It has the appearance of anything but an 

 Infusorian ; and in fact such a strong 

 resemblance does it offer, not only in form, 

 but also in habit, to some of the articu- 

 lated animals which are known as Roti- 

 fera, as to induce certain naturalists to 

 believe that it forms a transitional link 

 between the Infusoria and Articulata. A' 

 careful investigation of its structure, and 

 the relation of its organs to each other, 

 will convince the unbiased observer that 

 it is in every respect a true Infusorian, and that its resemblance 

 to the Rotifers is such as often occurs between animals other- 

 wise totally different, It is an infusorian between two leaves 

 or flexible shells (/, t, up, lw,} of unequal width, which are united 

 by a sort of hinge along the left border (h to t), and gaping to a 

 more than equal extent along the right side, where the upper one 

 (up] far overhangs the other (Iw, bk) throughout the whole length 



Fig. 99. Pleuronema instabilis, n. sp. 1000 diam. m, the mouth ; st, the 

 food gathered in one mass ; me, large cilia in the vestibule of the mouth ; /, the 

 single vibrating lash projecting from m ; cl, vibratory cilia covering the body in 

 rows ; si, the posterior, and sl l the anterior saltatory cilium ; cv, the contractile 

 vesicle ; n, the reproductive organ. Original. 



Fig. 100. Dysteria prorcefrons, n. sp. 600 diam. A view from the broader 

 side, h, t, up, the broader valve ; lie, the right edge of the narrower valve ; bk, 

 the beaks of the narrower valve ; rd, the ridges on the surface of the broader 

 valve ; pv, the pivot; I, the large, single vibratory lash; I 1 , vibratory cilia; 

 y, the jaws ; st, the mass of food ; cv, cv 1 , the two contractile vesicles ; n, the re- 

 productive organ. Original. 



Fig. 100. 



