360 DESCRIPTION OF [Rotatoria. 



bling a forked tail, and a rotatory organ, simply ciliated, 

 ,and disposed in bundles on the frontal region ; eight of the 

 larger species have numerous muscles ; eighteen or nine- 

 teen have two jaws, each furnished with a single tooth ; in 

 eight the jaws have many teeth ; the oesophagus is mostly 

 short, with a simple wide conical alimentary canal (coelo- 

 gastrica) ; in N. tuba only is there a stomach-like division, 

 with a constriction (gasterodela, a), and in N. myrmeleo, 

 syrinx, and clavulata, there is also a stomach-like enlarged 

 place, but no constriction (gasterodela, /3) ; coacal appen- 

 dages are observed only in N. clavulata. The two earlike 

 anterior appendages of the alimentary canal, regarded 

 as pancreatic glands, exist in twenty-four species. The 

 propagative system evidently is hermaphroditic in sixteen 

 species ; in the others the ovarium only is seen ; none are 

 viviparous : N. syrinx alone was observed by Ehrenberg 

 to contain fully developed ova. The vascular system is 

 represented, in ten species, by delicate tubes, with flexible 

 and tremulous gills ; only three of the smaller species 

 have gills : in N. myrmeleo and syrinx, a broad vascular 

 network is distinct about the head : a prominent respira- 

 tory (?) tube in the neck is present in four or five species ; 

 in some others an opening alone is seen. The visual point 

 is red, except in N. felis, where it is colourless ; a ganglion 

 is placed beneath the eye in twenty-six species. In N. 

 copeus and centrura, the brain is three-lobed, and placed 

 upon the head of the oesophagus ; in the rest it consists of 

 one or more nervous ganglia, situated amongst the vibra- 

 tile cilii-muscles of the frontal region ; free nervous threads 

 and ganglia are also observed in different members. This 

 genus is especially remarkable for the parasitical habits of 



