ig6 Introduction to Animal Morphology. 



fused parapodia. A few are sessile, tube-dwellers. 

 The tails of others contain glandular tissue, and may 

 end in a forceps of two blades for holding to foreign 

 bodies. Some have long, bristled, swimming feet, 

 three, six, or more (Triarthra, Hexarthra, Polyarthra). 

 Pedalion has beside its two trochal discs, two median 

 dorsal, two median ventral, two right lateral, and twa 

 left lateral appendages (imperfectly jointed r) like those 

 of Dinocharis, and moved by striped muscle ; it has 

 also two caudal ciliated lappets. 



The sexes are dimorphic, the males being few, 

 small, with no digestive organs except a rudimental 

 pharynx, but with a water-vascular system. The 

 azygos, saccular testis appears early in the embryonic 

 male, and the end of the vas deferens is protrusible as 

 a penis. The male may differ, even in shape of its trochal 

 discs, from the female. The females have a roundish 

 or crescentic ovary, an oviduct opening dorsally into 

 the cloaca, when such exists. The eggs are of two 

 kinds, thin-shelled in summer ; but as no males are 

 found at the time of their production, they constitute 

 an example of parthenogenesis. From some of these 

 eggs males develop, but they are always vastly fewer 

 than the females. The winter eggs are hard, and often 

 rough-shelled. The eggs have no primitive streak, 

 and develop slowly. The embrj^os are directly deve- 

 loped, varying only in the growth or disappearance of 

 organs. Floscularia has a worm-like lar\^a, with a 

 ciliary zone [Weisse). 



There are about 215, mostly freshwater, species, some of 

 •which bear drying, and revivify on moistening. 



Order i. Gasterodela* — body sacciform, with neither 



* Some make an order Gastrotricha for Ichthydium, Chsetonotus, &c. 

 Taphrocampa having a chewing apparatus, joins this to the true Rotifers. 



