CGELENTERA I A 



7' 



net 



possess a very 

 large number 

 of nettle cells ; 

 these are clearly 

 defensive. Sonic 

 resemble pol) ps 

 without tenta- 

 cles and without 

 a mouth, — they 

 are s u p p o s e d 

 to be merely 

 sensor}'. And 

 finally, some in- 

 dividuals serve 

 entirely for re- 

 production, pro- 

 ducing the germ 

 cells which give 

 rise to new 

 colonies. The 

 Siphonophora 

 are very beauti- 

 ful, being trans- 

 parent, with 

 brightly colored 

 spots here and 

 there, and while 

 some are small, 

 others attain a 

 great length. 

 They are par- 

 ticularly abun- 

 dant in tropical waters, floating on the surface of the ocean. 

 The Portuguese man-of-war, already mentioned (Fig. 53), is a 

 member of this order. 



Fig. 55. Diagram of a siphonophore; the thick line represents 

 the entoderm, outside of which is the ectoderm, and the cavity 

 within is the ccelenteron. cce, ccenosarc ; dz, dactylozooid ; hph, 

 hydrophy Ilium ; net, net' , nectocalyces ; n/c, battery of nematocysts ; 

 /, polyp; /;/, pneumatophore ; /, tentacle. (After Claus, from 

 Parker and Haswell's Text-book.) 



CLASS II. SCYPHOZOA 



The Scyphozoa (Gr. aKvfyos, a cup, and ^wov, animal) are all 

 marine and include both polyps and medusae, but these are very 



