76 GENERAL HI9T0EY OF 



very dilatable portion, opening externally, and which, from serving, 

 also, as a conduit for the eggs (in the female,) is analogous to the 

 cloaca of birds. It always opens at the base of the footlike tail. 



Every portion of the alimentary tube, except the muscidar bound 

 oesophageal bulb, is capable of great distension ; and this is particularly 

 noticeable in the crop, stomach, and cloaca, in the last, during the pro- 

 cess of oviposition, the eggs of Rotatoria being of very large size. 



A very curious exception to the general rule, of a digestive inlet 

 and outlet in Rotatoria, has been observed by Mr. Gosse, in the 

 genus Asplanchna, for it has "no anal orifice, nor any intestine 

 below the stomach ; the remains of the food, when digested, are 

 regurgitated by the contraction of the viscera, and discharged 

 through the mouth," as ia Polypes. 



Special organs of secretion exhibit themselves in this class, under 

 their simplest form, as sac's, or cells containing coloured fluid, and 

 opening into the alimentary canal. Attached to the oesophagus, or 

 to the upper part of the stomach, is a pair of glands, usually of an 

 oval form, but sometimes, though rarely, cylindrical or forked, and 

 considered by Ehrenberg, to represent the pancreas. Besides these, 

 coloured sacs, with yellowish brown, or greenish granular contents, 

 are often to be seen external to the stomach and intestine, into which 

 they pour their secretion by gall-ducts — as Ehrenberg thinks is 

 evident in Enteroplea — the secreting cells themselves being the liver, 

 on biliary glands. Siebold states that the pancreatic glands are absent 

 in the Idhydina; whilst in some species, as Notommata clavulafa, 

 Biglena lacustris, (fig. 403,) and MegalotrocJia albo-favicans, (figs. 

 374-376), they are complicated by additional sacs or tubes. 



In Asplanchna, Mr. Gosse describes " several yellow glandular (?) 

 spots, varying in number," on the top of the cushion of the oesopha- 

 geal bulb. In Floscularia campanulata, Dr. Dobie observed large 

 fixed granules distributed here and there, throughout the body and 

 tail, most nearly resembling globules of oil. 



The glandular bodies concerned in the process of reproduction are 

 described in the section devoted to the consideration of that process. 



The preceding account of the digestive system of Rotatoria, 

 applies, in the main, to the females only ; the recent discovery of the 

 male Rotatoria, has also shewn an organization, peculiar to them- 



