IV. CTENOPHORA. 



263 



mass of otoliths, supported on four bundles of S-shaped agglutinate 

 cilia. From these bundles of cilia eight bands of thickened epi- 

 thelium, at first in pairs (fig. 223, ws), later diverging, pass to the 

 oral pole (fig. 221, r). These meridional bands (so called from 

 their course) consist in part of ciliated epithelium, in part of the 

 characteristic ' combs ' which are the locomotor organs, and which 

 must be regarded as transverse rows of long agglutinated cilia. 

 The combs (fig. 219) arise from thick epithelial ridges, transverse 

 to the meridional bands, and are so far apart that the free edges 



FIG. 



FIG. 223. 



FIG. 222. Section of sense body of Cnllianira. A, through the centre ; 7?, excentric ; 

 d, roof of sensory groove ; /, support of otoliths, o ; p, pigment cell ; se, sensory 



FIG. 223. Aboral pole of Callianira bialata. (From Lang.) /, supports of otoliths, 

 o; PP, pole plate; sfc, sense body; to", openings of gastral funnels; ics, ciliated 

 bands- 



of one comb overlap the base of the next like shingles. In conse- 

 quence of their fibrous structure the combs are strongly iridescent 

 and in motion cause a beautiful play of metallic red, blue, and green 

 over the meridional bands. These combs act like oars and row 

 the body about. Since the combs begin some distance from the 

 aboral pole, they are connected with it by means of ciliated grooves 

 following the line of the meridional bands. Experiment shows 

 that the sense body is an organ of equilibration and of correlating 

 the action of the different rows of combs. 



The ectoderm gives origin to two more important organs, two 

 pole fields and two tentacles. The pole fields (fig. 221, p; 223, pp) 

 are two epithelial patches extending a short distance in the 

 sagittal axis from the sense body and possibly are olfactory or 

 taste organs. The tentacles arise, in the transverse axis, from the 



