406 



ROTIFERA. 



two strap-shaped sexual glands and contrac- tionary system is indicated ^by the presence of 

 tile vesicles. Traces of a vascular system are eyes, which are visible in ten genera and thirty- 



tile vesicles. 

 seen only in 



a few species. 



The sensa- three species. 

 Analysis of the genera. 



In this as in the preceding family, there can 

 be little doubt that the artificial character, 

 the number and position of the so-called eyes, 

 on which the genera are founded, separates 

 species which are united by much more im- 

 portant characters. Thus Dujardin remarks, 

 that the genera Lepade/la, Metopidia, Ste- 

 phanops, and Squamella are separated only 

 by characters which vary according to the 

 nutrition of the animal and the time of the 

 year. The same remark will apply to many 

 of the genera of the preceding family Hyda- 

 tinaea. The species of this family are found 

 in both salt and fresh waters, and have a 

 wide distribution over the surface of the 

 earth. The genus Lepadella is developed 

 sometimes in stagnant water in such quan- 

 tities as to give it a milky appearance. 



Family 7. PHILODIN^A. Character. 

 Naked Rotifers with two rotatory organs. 



The body of these animals is mostly of a ten- 

 inform, cylindrical, or spindle-shape, with false 

 articulations, by which, through its muscles, 

 the animal is enabled to withdraw the parts 

 of its body one within another, like the tube 

 of a telescope. The double rotatory organ, 

 so evident in Rotifers (Jig. 301 .), is seen in all 

 the species. In every species there is a fur- 

 cated foot. In the genera Callidina, Rotifer, 

 Actinunts, and Philodina, appendicular hooks 

 are found on the false articulations (fig. 295.). 

 A muscular system is seen in Callidina, Acti- 

 nurus, Rotifer, and Philodina. Three of the 

 genera have two jaws with two teeth, and 

 two jaws with a row of teeth. A filiform in- 

 testine, with a vesicular enlargement at the 

 end, is seen in four of the principal genera. 

 Intestinal glands are seen in four genera. 

 The reproductive system is hermaphrodite in 

 four genera, with an ovarium and male sexual 

 glands, and contractile vesicles. The last are 

 on\y seen in Rotifer and Philodina. These 

 two genera and Actinurus sometimes produce 

 living young. Traces of a vascular system in 

 the transverse vessels of Rotifer and Philodina, 

 and also in the respiratory tube or opening 



of these genera, and of Actinurus and Mono- 

 labis, are seen. Nervous masses are found 

 under the eyes. 



Fig. 295. 



Philodina roseola. (After Ehrenberg.~) 



a, respiratory tube ; b, alimentary canal ; c, cel- 

 lular mass; d, terminal intestinal pouch; e, anal 

 orifice. 



