ROTIFER A, THEIR GENERAL STRUCTURE. 



429 



FIG. 201. 



the second. Connected with the alimentary canal are various 

 glandular appendages, more or less developed ; sometimes clus- 

 tering round its walls as a mass of se- 

 parate follicles, which seems to be the 

 condition of the glandular investment 

 (g) of the alimentary canal in Rotifer; 

 in other cases having the form of coecal 

 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 intesti- 

 nal tube, have been regarded, and pro- 

 bably with correctness, as the rudi- 

 ment of a liver. In a curious animal- 

 cule of this class, minutely described 

 by Mr. Dalrymple, 1 although the 

 mouth, masticating apparatus, and 

 stomach are constructed upon the re- 

 gular type of the genus Notommata, 

 to which it seems nearly allied, yet 

 there is neither intestine nor anal ori- 

 fice, and the indigestible matters are 

 rejected through the mouth. This, 

 so far as is yet known, is a solitary 

 example of the existence of this cha- 

 racter of degradation in the class Ro- 

 tifera. There does not appear to be 

 any special circulating apparatus 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 in- 

 ner tegumentary membrane, is probably to be regarded as nu- 

 tritive in its character; and its aeration is provided for by a 

 peculiar apparatus, which seems to be a rudimentary form of the 

 u 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 flexuous tube (Fig. 200), which extends from 

 a contractile vesicle common to both and opening into the cloaca 

 (Fig. 201, , 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 corresponding 

 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 



1 " Philos. Transact." 1849, p. 339. 



Rotifer vulgaris, as seen at A, wilh 

 the wheels drawn in, and at B with ihe 

 wheels expanded; a. mouth; 6, eye- 

 spots ; c, wheels ; d, calcar (antenna ?) : 

 e,jaws and teeth; /, alimentary canal ; 

 >j. glandular (?) mass enclosing it; A, 

 longitudinal muscles; i, t, tubes of 

 water vascular system; k, young ani- 

 mal; /, cloaca. 



