llfFrSCBTAI. ANIMAI.CXTLES. 47 



that of Insects and Crustaceans, to animals presenting nothing but 

 difPiised coloured specks. 



" Such spots, whether in number or position, have so little 

 physiological importance in the Planaria?, and in certain Annelides, 

 that they are often not even to be employed as an absolute specific 

 character. In the Rotatoria, the analogy with which is more 

 especially insisted on, these pigment spots are, in some species, 

 known to disappear from age, and in others to become more evident, 

 in proportion to size or development of individuals : so that the 

 learned micrographer of Berlin, in his attempt to base the generic 

 characters of these animals on the presence and number of the eyes, 

 has been led to place in different genera, species very closely allied, 

 if not identical. Indeed, that a black or red colour is in general an 

 attribute of the pigment of eyes, cannot be a reason for concluding 

 an eye to exist wherever there is a red colour ; if so, indeed, we 

 must accord them to some intestinal worms, such as the Scolex 

 polymorphus, which has two red spots on the neck ; to the actiniae, 

 which are often strewed with such specks , and also to some bivalved 

 mollusks." 



"If the ability of the Infusoria to direct their course through the 

 liquid, and to pui'sue their prey, be appealed to ia evidence, it is 

 certainly, in the fii'st place, necessary to verify the reality of this 

 faculty, which I think equally fabulous with all related concerning 

 the iustiucts of these animals. Indeed, it would not even prove the 

 red specks to be eyes, since the greatest number of Infusoria 

 supposed to be endowed with such a faculty, are in want of them ; 

 and those which do possess them, do not exhibit that power ia a 

 higher degree of development." 



M. Ehi'enberg, following up his line of reasoning, after having 

 assumed the signification of the red points, has recourse to thi» 

 assumption, to demonstrate the ti'ue nature of certain white sj)ecks, 

 more or less distinct, which he supposes to represent nervous- 

 ganglions, — " These specks are the only parts of a nervous system 

 spoken of as seen, the rest is altogether furnished by analogy." 



Siebold, "Wagner, and others, concur with M. Dujardin in denying 

 the visual character of the coloui-ed spots of Infusoria, as weU as the 

 presence of nerve matter in an isolated form. 



