ROTIFERA. 



413 



canal is constructed into a bag or stomach, as 

 Brachionus. 



4. Trachelocystica, with a simple alimentary 

 canal, enlarged at the lower part, as in 

 Rotifer. 



The upper part of the alimentary canal be- 

 low the jaws is called by Ehrenberg the oeso- 

 phagus, and is said to be either long or short, 

 according to the distance which intervenes 

 between the jaws and the further enlargement 

 of the alimentary canal. In some cases, as in 

 Stephanoceros (/g.292. c), there is an enlarge- 

 ment anterior to the origin of the jaws, which 

 is called the crop or gizzard. Into this cavity 

 the food is taken before it passes into the 

 lower portions of the alimentary canal. The 

 same organ is seen in Floscularia. In this 

 animal it is evidently clothed with vibratile 

 cilia, whose movements seem to make up for 

 the deficiency of a true rotatory apparatus. 

 The whole of the alimentary canal seems to 

 be lined with vibratile cilia, for although they 

 are too minute, in most instances, to be seen, 

 yet the movement of objects in the interior of 

 the canal, as well as the force and direction 

 with which substances are occasionally pro- 

 pelled from the oral orifice, would lead to this 

 conclusion. The whole of the alimentary 

 canal is often inclosed in a mass of cellular 

 substance, as seen in Philodina roseola {fig. 

 295. c), and Dinocharis panpera (fig. 302.). 



Fig. 303. 



Notommata myrmeleo. 



a, the single eye ; b, oesophagus ; c, alimentary 

 canal ; d, d, muscular fibres ; e, e, glands ; f, f, re- 

 spiratory processes ; g, sexual tubes (male ?) ; n, 

 germinal vesicle in ovum ; t, ovarium ; k, vascular 

 network. 



Attached to the intestinal tube, and ap- 

 parently enlargements of its walls, are various 

 appendages, about whose functions there is 

 much difference of opinion. The most con- 

 stant of these bodies are seated on each side 

 of the termination of the oesophagus. They 

 are mostly two in number, one on each side 

 (fig. 297. c y c ; fig. 289. c,c ; fig. 296. h, /;.) 

 Sometimes they are four in number, as in A r o- 

 tommata myrmeleo (fig. 303. e, e), and in other 

 cases more numerous. Ehrenberg originally 

 regarded these as spermatic glands, but, sub- 

 sequently, he called them pancreatic glands. 

 Grant and others have called them indif- 

 ferently pancreatic or salivary glands ; and if 

 they are secreting organs at all, they probably 

 perform the functions of these glands in higher 

 animals. Seated lower down the alimentary 

 canal than these, are sometimes seen other 

 projections, having the appearance of follicles, 

 and these have been supposed to secrete 

 bile. Dr. Grant describes what we have called 

 a cellular mass in Philodina roseola, as a 

 number of " short, straight biliary follicles," 

 such as are seen in many of the higher forms 

 of Annelides. Professor Rymer Jones re- 

 gards the superior as well as the lower of 

 these appendages, as the " first rudiments of 

 a liver." Dujardin is inclined to regard these 

 appendages rather as caeca than glands. 



Vascular and respiratory systems. Al- 

 though Ehrenberg has pointed out several 

 structures in the Rotifera as indications of 

 a vascular system, it is very questionable 

 whether any circulation takes place through 

 vessels at all. In Hydatina senta (fig. 293.), 

 Notommata myrmeleo (fig. 303.), Rotifer vul- 

 garis (fig. 299.), and many others, can be seen 

 a series of transverse bands, lying directly 

 under the tegument ; in Hydatina senta, these 

 are connected with a longitudinal band, and 

 these are regarded as a dorsal vessel and its 

 branches. Doyere, with much propriety, re- 

 gards these as a musculo-cutaneous system, 

 analogous to a system of the same kind 

 which he has described in the tardigrade 

 Infusoria. In Hydatina senta, Notommata 

 myrmeleo, and some other species, there are 

 some free longitudinal cords, connected with 

 a fine vascular network near the mouth, and 

 which send filiform prolongations to the ali- 

 mentary canal, which Professor Owen thinks 

 may, with more probability, be regarded as 

 " sanguiferous organs." We must, however, 

 express our doubts as to the existence of a 

 vascular system in these animals at all. In 

 some of the Rotifera, internal tubes are seen, 

 called by Ehrenberg seminal tubes, and upon 

 these are often placed a row of little project- 

 ing tremulous processes, on which he has be- 

 stowed the name of gills. These processes 

 are not very numerous in Hydatina senta 

 (fig. 293.) ; but they are more numerous in 

 Notommata myrmeleo (JZg.3Q3.f,f). The 

 tubes on which these gills are placed, com- 

 municate in some instances with vessels at 

 the back part of the neck, which are again in 

 relation with the siphon to which we have 

 before alluded, and the whole is supposed to 



