OF THE ROTATORIA. 



649 



in the form of hooks ; posterior, of 

 straight styles. 1-20". Marine, among 

 corallines. 



C. polypoda (xxvi. 30 a, b, c). — Oval, 

 sinuous in front ; convex above, and 

 marked with from 7 to 8 narrow ribs; 

 flat below, and funiished with numerous 

 long and flexible styles. In stagnant 

 sea-water. 



C. Cicada. — Oval, very convex above, 

 granular, without costae ; margin round- 

 ed ; concave beneath, and there provided 

 with long and flexible styles. Appears 

 the same as the Trichoda Cicada of Miiller, 

 but not as its supposed synonym Oxy- 



tricha Cicada (Ehr.), which is like the 

 Coccudina costata rather than C. Cicada. 

 1-812". 



C (?) Cimex = Stylotujchia Cimex(Ela.v.). 



C. reticidata. — A name provisionally 

 applied to an animalcule found in the 

 Seine, having a granular and reticulated 

 surface, and large styles at each end. 

 1-578". 



Q. crystallina (Perty). — Hyaline, with 

 from 6 to 7 long costae on the dorsum, 

 and very short cilia. Outline roimd. The 

 costse are less elevated than in C costata. 

 Wet moss and turf on the Alps. 1-900" 

 to 1-600". 



OF THE GROUP ROTATORIA (p. 392). 



(Plates XXXII.-XL., and part of XXY.) 



Those animalcules which are included in the great di\dsion Rotatoria are 

 either destitute of a nervous system, or have merely an isolated ganglion 

 near the head, representing the brain, with a few nervous threads proceeding 

 from it to the body. They have no pulsating heart, nor true blood-vessels in 

 which the blood circulates. The fluid apparently representing the blood 

 occupies the cavity of the body and bathes the external siu'faces of the various 

 viscera, as in the lower Crustacea. The alimentary canal is tubular, variously 

 constricted at intervals, often di\4dcd into segments, each of which appears to 

 perform special functions. One segment, near the ujDper extremity of the 

 canal, is pro\^ded with a pair of moveable appendages, between which all the 

 food swallowed has to pass, and which may be regarded as teeth or jaws, 

 probably analogous to the gastric teeth of Crustaceans. In many species 

 there are csecal prolongations of the stomach ; whilst the walls of the^organ are 

 thick and cellular, having a glandular aspect. The alimentary canal is, mth 

 some remarkable exceptions, furnished with an orifice at each extremity, or 

 mouth and aniLS, — the latter usually opening into a cavity termed the cloaca, 

 or common outlet for the intestine, the oviduct, and the (so-called) water- 

 vascular canals. The interior of the canal is variously supplied with cilia, 

 which are in constant motion. The caecal and cellular appendages are sup- 

 posed to be glandular ; but their functions, as well as relations to the liver 

 and other chylopoetic organs of higher animals, are doubtful. 



The character and instruments of the respiratory functions in the Rotatoria 

 ai-e alike doubtful, but most probably they are performed by the water vas- 

 cular canals. These are two slender tubes (XXXYI. 6 e,(j) springing fi'om 

 the cloaca near the anal outlet, and proceeding upwards on each side of the 

 intestine towards the head, where they branch, and sometimes the two 

 anastomose, at others probably terminate in cuh-de-sac. These canals com- 

 mence at a pulsating organ (XXXYI. 6 v ; XL. 5), common to both, and 

 connected with the cloaca. In various parts of their course they are fur- 

 nished with pyriform appendages (XXXYI. 6 a) (tags) varying in number 

 from two to eight on each side. In the interior of each tag is a single 

 large cilium, which exhibits an incessant motion, resembling the flickering 



