46 



LECTURE 111. 



chionus, and Pterodina. In all the species the shell is a cylinder or 

 case (testula), not a mere shield (scutellum). Horn-like processes 

 project from the front margin of the firm shell in some species of 

 Brachionus, and from both front and back margins in other species. 

 In some Notei and Anurcece the shell is ornamented by large pen- 

 tagonal or hexagonal groups of granules. 



The cephalic cilia are aggregated into from two to five groups, upon 

 lobes {fig. 20, a\ or pedunculate discs, which in some species are 

 developed into short tentacular processes, with a verticillate arrange- 

 ment of cilia, as in Floscularia and Stephanoceros {fig. 22.). These 

 lobes or processes Ehrenberg regards as muscular. The movements 



of the ciliated quasi-wheels are 

 under the control of the will. They 

 can be instantly arrested, the whole 

 apparatus drawn out of sight, 

 again pi'otruded, and as instantly 

 set in motion. The muscles which 

 protrude and retract the ciliated 

 lobes, which bend and modify the 

 form of the body, and which throw 

 out, attach, or heave in the anal 

 anchors, are developed in the form 

 of distinct narrow fibrous bands, 

 which are transversely striated. 

 The long and narrow longitudinal 

 muscles which retract the head and 

 shorten the whole body are some- 

 times in two pairs, one lateral and 

 the other dorsal {b,fig. 20.). There 

 are other mere filamentary longitudinal muscles, which are usually 

 forked at their insertions. Very fine muscular threads are attached 

 to the principal viscera, and keep them in their places. The antagonist 

 transverse bands which diminish the breadth of the body and restore 

 its length, are shown at c c, fig. 20. All these muscles are attached 

 to an inner layer of the skin separable from the outer one. 



With this advanced condition of the muscular system the parts of 

 the nervous system now likewise become distinctly visible. Ehren- 

 berg delineates a large cerebral ganglion, which in some species is of 

 a trilobate form, in others {fig. 22, b) is double, and which is always 

 in close connection with the coloured, generally red, ocellus or eye- 

 speck {fig. 20, e, fig. 22, a). Some of the nervous filaments ex- 

 tend from this ganglion forwards to the muscular lobes supporting 



Notommata. 



