324 



ZOOLOGY 



length, and is divisible into two distinct parts — a broad anterior 

 region, the trunk, and a slender movable tail (t.). The trunk is 

 enclosed in a glassy cuirass or lorica (lr.), formed by a thickening 

 of the cuticle and produced into several spines : the tail is 

 wrinkled superficially and ends in two slender processes, together 

 forming a kind of forceps. One surface of the trunk is flattened, 

 and owing to the position of the mouth, is considered as ventral, 



Fig. 264. — Brachionus rubens, female. A, from the dorsal aspect ; B, from the right side. 

 a. anus ; br. brain ; d. j. dorsal feeler ; c. gl. cement-gland ; cl. cloaca ; c. I. ciliary lobes ; c. v. 

 contractile vesicle ; e. eye-spot ; int. intestine ; lr. lorica ; I. f. lateral feeler ; m. muscular 

 bands ; nph. nephridial tubes ; ov. germarium ; ph. pharynx ; st. stomach ; t. tail ; tr. d. 

 trochal disc ; vt. vitellarium. (After Hudson and Gosse.) 



the opposite or dorsal surface is convex both from before back- 

 wards, and from side to side. 



The anterior portion of the body projects from the lorica in the 

 form of a transverse disc (tr.d.) with a prominent edge fringed with 

 cilia : this is the trochal disc, and is one of the most characteristic 

 organs of the class. By the action of the cilia the animal is 

 propelled through the water, and, as in Vorticella, their successive 

 flexion gives an appearance of rotation to the disc or " wheel- 

 organ " whence the name of the class is derived. Within the circlet 

 of cilia arise three prominences (c.l.) covered with cilia of large 



