ROTIFER A. 



stomach met with in the Crustacea, to which the rotifera will be 

 found gradually to approximate. 



(162.) Notwithstanding the microscopic size of the Rotifera, and 

 the consequent difficulty of detecting the more minute details of 

 their structure, Ehrenberg thinks he has succeeded in discovering 

 filamentary nerves, and even nervous masses, distributed in different 

 parts of their body ; an arrangement which not only would account 

 for the complete association of their voluntary movements, but 

 would, from the presence of ganglia, 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 (Jig. 49 and 50, c) ; 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 connection with a nervous mass, 

 which, from examining his drawing of the arrangement of the 

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



(163.) The nervous system of Notommata clavulata, as describ- 

 ed by this indefatigable observer, is represented in fig. 51. It would 

 seem to consist of several minute nodules, exhibiting a somewhat 

 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. 



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 rotifera 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 engrav- 

 ing has been accurately copied. 



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 con- 

 centration of nervous energy. The position of the ganglia depicted 

 in the figure as being in relation with the nervous threads would 



