CIIVrTER SECOND 



ACALEniS AS A CLASS. 



SECTION I . 



MODE OF DETERMINING THE NATURAL LIMITS OF THE CLASS. 



Fig. 1. 



After -what lias lieon said, in the first volume of this work, resjiectiiif systom.s 

 in Zoology, it is hardly necessary to repeat here, that no arljitrary arrangement 

 of animals can ever constitute a natiu-al classification. Were it 

 not so, every naturalist might present an arrangement suited to 

 his individual views, and for which he would have as much 

 authority as any one else. The absurdity of such a view, when 

 clearly stated, is at once obvious. And yet most classifications 

 have no better foundation for their details than a vague 

 feeling of appropriateness in the minds of their authors. The 



class of Acalephs, however, has presented 

 particular difficulties to systematic writers ; 

 and it is not too much to say, that there 

 are no two naturalists, conversant with the 

 animals belonging to this t>pe, who agree in 



Fig. 2. 



Pl-L\( H < \ \M 1 L\, 



r< 1 mil LcS 

 a a Umbrella. — m m Mouth 

 tentacles, or arms ; the pro- 

 longation of the angles of tlicir aiTaugemeut of them. Nay, the lim- 



the mouth, 

 tentacles. 



Marginal 



its of this class are by no means clearly 

 determined; for, while some unite under that name only the 



free moving gelatinous Radiata {Fig. 1), others would asso- "'■"''™:"";^';'"■"-'f'; tf 



'-' ^ \ u jy a a Sterile mOividuals. — & Fertile 



ciate with them a number of pedunculated individuals and ^°^i™i"^>' producing nmi.. mo- 



^ uusas. — d Clusters of uiale Mf- 



fixed communities of animals somewhat allied to Polvns (Ffa *'"-'^«'--oo Probosds, with the 



.1 \ tJ mouth at the apex. — t Klongateil 



2), and actually united with Polyps by some naturalists t™t«ies of the steriie indivwu- 



^ *' V'' 1 ^' alri ; m the fertile one &, they arc 



Again, some refer to the class of Polyps all the compound --tapie knobs upon the probes™,,. 



