308 ORGANS OF DIGESTION. 



different genera. In the vorticella citrina (Fig. 107- B.) the 

 intestine (b, c, d, e.) passes downwards without dilatation, 

 and after bending round in the lower part of the body, 

 it ascends more narrow to terminate at the same lateral 

 oral funnel-shaped ciliated aperture (B. a.) at which it 

 commenced, having numerous coecal dilatations or stomachs 

 (B. f.) communicating with its interior throughout its 

 whole course. This circular form of intestine, opening at 

 both its extremities in the same ciliated aperture, is per- 

 ceived also in the carchesium, zoocladium, ophrydium, vagini- 

 cola, and other genera, which from this character form the 

 group termed cyclo-cala. In some animalcules of this 

 group, as in the stentor polymorphus, (Fig. 107- C.), the 

 circular intestine is regularly sacculated, or alternately 

 dilated and contracted, throughout its whole course 

 (C. b, c, c, d.), and from these dilated parts the little 

 stomachs (C. f.) take their origin. In other species of 

 stentor the intestine is twisted in a spiral manner through- 

 out its circular course. Many of the polygastric animalcules 

 which approach nearer to the helminthoid classes in 

 the lengthened form of their body, have the mouth and anus 

 placed, as in higher classes, at the opposite extremities of 

 the trunk, as seen in the enchelis pupa (Fig. 107. D0> where 

 the intestine, passing straight and cylindrical through the 

 body, from the wide ciliated terminal mouth (D. .), to the 

 opposite dilated rectal termination (D. .), gives off very 

 numerous coecal cavities (D. /, /.) along its whole course. 

 Such animalcules form the group termed ortho-coela from 

 the straight course of the intestine. In others, however, as 

 the leucophrys patula (Fig. 107. E.), the intestine passes in 

 a spiral course through the short and broad trunk of the 

 animalcule, giving off digestive coeca (E. f.} in all parts of 

 its course, from its ciliated wide oral extremity (E. a.) to the 

 saccular rectum (E. b.) at the opposite end, and such animal- 

 cules as present this spiral form of the alimentary canal com- 

 pose the group of campylo-ccela, of which there appear to be 

 few known genera. About thirty-five genera of polygastric 

 animalcules appear to have an intestine of some form (ente- 

 rodela), passing through their transparent body, and deve- 

 loping from its parietes minute globular coeca, which are 

 regarded as stomachs, from the quickness with which the 



