474 INTERNAL STRUCTURE OF ROTIFERA. 



tiuction between the stomach and intestinal tube, the former being 

 a large globular dilatation immediately below the jaws, whilst the 

 latter is cylindrical and comparatively small. The alimentary 

 canal of Rotifer (Fig. 244) most resembles the first of these types, 

 but presents a dilatation (/) close to the anal orifice, which may be 

 considered as a cloaca ; that of Brachionus (Fig. 243) is rather 

 formed upon the second. Connected with the alimentary canal 

 are various Glandular appendages, more or less developed ; some- 

 times clustering round its walls as a mass of separate follicles, 

 which seems to be the condition of the glandular investment (</) of 

 the alimentary canal in Rotifer ; in other cases having the form 

 of cascal tubuli. Some of these open into the stomach close to the 

 termination of the oesophagus, and have been supposed to be 

 Salivary or Pancreatic in their character, whilst others, which dis- 

 charge their secretion into the intestinal tube, have been regarded, 

 and probably with correctness, as the rudiment of a Liver. — In a 

 curious animalcule of this class, minutely described by Mr. Dai- 

 ry mple,* although the mouth, masticating apparatus, and stomach 

 are constructed upon the regular type of the genus Notommata, 

 to which it seems nearly allied, yet there is neither intestine nor 

 anal orifice, the indigestible matters being rejected through the 

 mouth. This, so far as is yet known, is a solitary example of the 

 existence of this character of degradation in the class Rotifera. 



359. There does not appear to be any special Circulating Appa- 

 ratus in these animals ; but the fluid which is contained in the 

 'general cavity of the body,' between the exterior of the alimentary 

 canal and the inner tegumentary membrane, is probably to be re- 

 garded as nutritive in its character ; and its aeration is provided 

 for by a peculiar apparatus, which seems to be a rudimentary form 

 of the ' water- vascular system,' that attains a high development 

 in the class of Worms. On either side of the body there is usually 

 to be observed a long fiexuous tube (Fig. 243), which extends 

 from a contractile vesicle common to both and opening iuto the 

 Cloaca (Fig. 244, i, i) towards the anterior region of the body, 

 where it frequently subdivides into branches, one of which may 

 arch-over towards its opposite side, and inosculate with a corre- 

 sponding branch from its tube. Attached to each of these tubes 

 are a number of peculiar organs (usually from two to eight on each 

 side), in which a trembling movement is seen, very like that of a 

 flickering flame ; these appear to be pear-shaped sacs, attached by 

 hollow stalks to the main tube, and each having a long cilium in 

 its interior, that is attached by one extremity to the interior of 

 the sac, and vibrates with a quick undulatory motion in its cavity ; 

 and there can be little doubt that their purpose is to keep-up a con- 

 stant movement in the contents of the aquiferous tubes, whereby 

 fresh water may be continually introduced from without for the 



* " Philosophical Transactions," 1849, p. 339. 



