

NERVOUS SYSTEM. 441 



would render these animals capable of possessing some of the local 

 senses ; indeed, Ehrenberg imagines he has discovered such to exist in 

 the shape of red specks, to which he gives the name of eyes. The organ 

 alluded to is a minute red spot, indicated in the figures (figs. 225 and 

 230) ; nevertheless no organization has been described of such a nature 

 as to entitle us unhesitatingly to designate it an organ of vision, even 

 if it should, as he intimates, invariably be in connexion with a nervous 

 mass, which, from examining his drawing of the arrangement of the 

 nerves, we should have little expected to be the case. 



(1140.) The nervous system of Notommata clavulata, as described by 

 this indefatigable observer, is represented in fig. 230. It would seem 

 to consist of several minute nodules (fig. 230, i i), exhibiting a some- 

 what symmetrical arrangement, and disposed apparently in pairs ; some 

 of these nodules, which are about ten in number, communicate with 

 each other by delicate filaments, whilst others seem to be quite insulated 

 from the rest. 



(1141.) Every one who is acquainted with the difficulty of conducting 

 microscopical observations, especially with the high powers needful in 

 detecting structures so minute as the nerves of the Rotifera, will be 

 exceedingly cautious in admitting the complete establishment of facts 

 involving important physiological principles ; and we cannot help 

 thinking that Ehrenberg has been misled by some appearances which 

 it is impossible for the most correct observer always to guard against, 

 in assigning to the Rotifer a an arrangement of the nervous system so 

 totally different from what is met with in any other class of animals as 

 that represented in his figure, from which our engraving has been ac- 

 curately copied. 



(1142.) All our ideas of the physiology of the nerves would lead us to 

 suspect some error. The uses of ganglia, as far as we know at present, 

 are either to associate nerves derived from different sources, or to serve 

 as centres for perception, or else they are for the concentration of ner- 

 vous energy. The position of the ganglia depicted in the figure as being 

 in relation with the nervous threads would scarcely seem to be consistent 

 with either of the above offices; and therefore we cannot but regard the 

 observations that have been hitherto recorded concerning the nervous 

 system of the Eotifera as far from being complete. 



(1143.) Professor Williamson observes that these small organs, which 

 are so common amongst the Eotifera, and which Ehrenberg regards as 

 nervous ganglia, are abundant in the Melicerta, but they afford no coun- 

 tenance to the hypothesis of the great Prussian Professor. They appear 

 to be nothing more than small cells or vesicles, formed of granular viscid 

 protoplasm, very similar to those into which the yelk of the egg becomes 

 divided. Sometimes they float freely in the fluid which distends the 

 integument and bathes the viscera ; at others, thin ductile threads pass 

 from one vesicle to another, as represented in fig. 229, h, where these 



