404- 



ROTIFERA. 



Although, at first sight, this might appear 

 a very natural group, a little examination of 

 their so-called rotatory organs will suggest 

 the propriety of separating from the rest the 

 genera Floscularia and Stephanoceros. The 

 organs which are called rotatory in those ge- 

 nera are evidently, as Dujardin has pointed 

 out, more like to the bristles or setae of the 

 lorica of other species, than to the true rota- 

 tory organs. The cilia, as they are called, of 

 Floscularia, do not move at all. The bristle- 

 like organs of Stephanoceros are covered with 

 cilia, which appear to be vibratile. The lo- 

 ricae of these animals also consist not of the 

 integument rendered horny, but of a case 

 secreted from the outside of the body of the 

 animal. The animal has the power of retiring 

 into this case, and in Stephanoceros this habit, 

 combined with its structure, give to it a strong 

 resemblance to some of the Cilio-brachiate 

 Bryozoa. This external resemblance is so 

 great, that many of the earlier observers re- 

 ferred it to the Polypifera. Oken referred it 

 to the hydroid polyps, and placed it between 

 Hydra and Tubularia. Goldfuss referred it to 

 a position in the same class between Coryna 

 and Cristatella. 



In the genus Lacinularia, the same ten- 

 dency to association exists, as is found in 

 Conochilus. 



The genera Floscularia and Stephanoceros 

 constitute the first family of Dujardin. The 

 remaining genera, previously noticed in this 

 and the other families, are referred to his 

 second family. 



Family 5. HYDATIN^A. Character. Na- 

 ked Rotifers, with a many-parted rotatory 

 organ. 



All the species of this family agree in the 

 divided condition of their wheels, which do 

 not consist of a circular or semi-circular row 

 of cilia, but of several distinct rows or circles 

 of such cilia, which are distinctly separated 



from each other. All the three forms, except 

 Polyarthra, have an elongated pincer-like pro- 

 cess, proceeding from the abdomen, which 

 resembles a tail, but is no proper continuation 

 of the dorsal integument. In many species, a 

 muscular apparatus is visible, by * which the 

 form of the body is changed. The nutritive 

 organs in all cases are very obvious. It is 

 mostly a simple conical intestine, which, in 

 the great proportion of species, is without the 

 constriction, which forms a kind of stomach 

 (fig . 293. d). Triarthra longiseta (fig. 297.) is, 

 however, an exception, and exhibits a stomach 

 formed by the constriction of the alimentary 

 canal ; whilst Notommata myrmeleo (fig. 303. c) 

 with some other species have a kind of gastric 

 enlargement, terminated by a narrow anal ori- 

 fice. The commencement of the alimentary 

 canal, with one or two exceptions, in all 

 the genera, is supplied with jaws and teeth . 

 Pancreatic glands are constantly present. 

 The reproductive system is hermaphrodite. 

 The ovarium (fig. 303. i) is elongated ; the 

 eggs few. The male organs consist of two 

 filiform elongated glands (fig. 303. g), and two 

 contractile vesicles. The ova appear under 

 two forms, one smooth and soft, the other 

 hard and spinous. Notommata brachionus, 

 and the genera Polyarthra and Triarthra, bear 

 their ova, like the Crustacea, attached to their 

 sides. In several of the genera a vascular 

 system has been observed (fig. 293. /,//,/), in 

 the form of transverse and longitudinal vessels, 

 the latter supplied with the tremulous organs 

 called gills ( fig. 303. /, /). With this system, 

 a kind of tap, or simple opening, in the neck 

 (fig. 293. g) is connected. In fifteen of the 

 genera, the two eyes, with their accompanying 

 nervous ganglia ( fig. 293. c), indicate the exist- 

 ence of a sensationary system. In Hydatina 

 and other genera, nervous ganglia are seen in 

 other parts of the body. 



Eyeless. 



With eyes. 



No teeth. 



f Teeth 



One eye. 



Two eyes. 



Three eyes. 



Eye frontal. 



Eye in neck. 



Eyes frontal. 

 Eyes in neck. 



Analysis of the genera. 



Foot styliform. 



[Without either, 

 divided! 



j"A furcate foot. 



No foot, 

 fins. 



[Styli 



liform foot. 



/Bearded. 

 [Not bearded. 



Foot furcate. 

 fin neck. 

 Two frontal, one! 



d.i-i 



,nj 



in neck. 



Two frontal pedi-1 

 culated, one 

 neck sessile. 



Eyes more fin single heaps. 



than three. [In two heaps. 



This family contains a larger number of 

 species than any of the others. They are 



Enteroplea. 



Hydatina. 

 Pleurotrocha. 



Furcularia. 



Monocerca. 



Syncfiteta. 



Scaridium. 



Notonimata. 



Polyarthra. 



Diglena. 



Triarthra. 

 Rattulus. 



Distemma. 

 Triophthalm us. 



Eosphora. 

 Otoglena. 



very generally diffused ; and Ehrenberg, in his 

 microscopic labours, in many parts of the 



