92 



ZOOLOGY. 



Class III. — Cteitophora (Comb-iearers). 



General Characters of Ctenoph.ores. — These beautiful an- 

 imals derive their name Ctenophora, or '" comb-bearers,"" 

 from the vertical rows of comb-like paddles (ctenophores) 

 situated on meridional bands of muscles which serve as lo- 

 comotive organs, the body not contracting and dilating us 

 in the true jelly-fishes. In tlieir organization they are 

 more complicated than the Aclinozoa, as they have a true 

 digestive cavity passing through the body-cavity, with two- 

 posterior outlets (it will be remembered 

 that Ceriantlius has one at the end of 

 the body). From this alimentary canal 

 are sent ofE chymiferous or water- vascu- 

 lar canals (Fig. 61) which correspond in. 

 their mode of origin with the water- 

 tubes of the Echinoderms. .\s regards 

 the rows of ])addles, each vertical row 

 consists of a great ntimber of isolated, 

 transverse, comb-like fringes placed one 

 above the other, and movable, either 

 isolately or in regular succession or 

 simultaneously (Agassiz). As tliese rows 

 of paddles are connected for their wliole 

 _, „, ^. . ^, length ^vith a chymiferous tube, thev 



Fig. 61. — View of the ^ ..*',. 



gastro-vascniarcanais of a probablv aid in respiration. Tliese ani- 



PfeKro6racAio,fromwhich ^ ^ . 



the two retractue aims mals also Stand mucli li]gher in the scale 



have been removed. A, „ ,.■ ,■, ,i ,, nix i n 



from one side, the month- ot liie than the Other Lffilenterates by 



opening above; B, seen -i • iii-i^ixi ti 



from the month-end.— bcmg more truly bilateral, the radial 



After Gegenbanr. 



imetrv so marked in the Actinia or 



in the jelly-fish being in these animals less apparent, as the 

 parts are developed on opposite sides of a median plane. 

 The nervous system, as originally described by Grant, con- 

 sists of a ganglion situated at the aboral end (end opposite 

 to the mouth) of the Pleurohrachia, from which, among 

 other nerves, eight principal ones are distributed to the 

 eigh^ rows of paddles. A nerve also proceeds to the so- 

 called otolitic sac (lithocyst) seated upon the ganglion. 

 Eimer has latelv shown that the nervous svstem of the- 



