118 



ROTIFERA. 



The character whence the class obtains its name is derived from 

 the peculiar organs placed upon the anterior part of the body, 

 which are subservient to locomotion, and assist in the prehension 

 of food ; these consist of circlets of cilia variously disposed in the 

 neighbourhood of the mouth, and having, when in action, the ap- 

 pearance of wheels spinning round with great rapidity, so as to pro- 

 duce strong currents in the surrounding water. Yet, notwithstand- 

 ing this peculiar structure of the locomotive apparatus, the ROTI- 

 FERA present very marked relations with the BRYOZOA, described 

 in the last chapter ; and the conversion of the ciliated tentacula of 

 the latter into the rotatory organs of the present class is effected 

 by several intermediate forms, which would seem to indicate a 

 closer alliance between the two than, from an examination of the 

 more typical genera of each, we should be inclined to suspect. 



(J54.) The annexed engraving of the Stephanoceros Eichornii* 



Fig. 48. 



(jig- 48) exhibits an 

 animal that would seem 

 to be one of the connect- 

 ing links by which this 

 transition is accomplish- 

 ed ; the transparent cell, 

 and ciliated tentacula 

 around the mouth, would 

 indicate this creature to 

 be a BRYOZOON ; but the 

 tentacula are no longer 

 the stiff and slender arms 

 which we have seen in 

 Bowerbankia, but are vi- 

 sibly stunted and thick- 

 ened at their base, thus 

 approximating in character 

 the cilia-bearing lobes of 

 a Rotifer ; while the inter- 

 nal organs, the pharynx, 

 gizzard, and stomach, in 

 this animal conform ex- 

 actly to the type of structure common to the Rotifera properly so 

 called. 



(155.) The body of one of the wheel animalcules is enclosed in 



* Ehrenberg. 



