IV 



PHYLUM CCELENTERAT^ 



181 



As in the lower Coronata, the margin of the umbrella bears four tentacles 

 (t.) and four tentaculocysts (tc.} but the position of these organs is reversed, the 

 tentaculocysts being per-radial, the tentacles inter-radial. The tentaculocysts 

 are set in deep marginal notches, and the tentacles spring from conspicuous 

 gelatinous lobes (I.}, which probably answer to the pedal lobes of the preceding 

 order. These pedal lobes sometimes bear a number of supplementary tentacles. 



gon. 



B 



endMtm 



circ. 



FIG. 134. Charybdsea marsupialis . A, side view of the entire animal ; B, vertical section 

 passing on the left side through an inter-radius, on the right through a per-radius ; 

 C, transverse section, circ. c. circular canal; <in<(. lam. endoderm lamella; cn<L lam', its pro- 

 longation into the velarium ; g. f. gastric filaments ; gon. goiiad ; gon'. septum separating 

 gonads ; f. lappet ; m>ib. manubrium ; rod. p. radial pouch ; t. tentacle ; tc. tentaculocy.st ; 

 vl. velarium. (After Claus, somewhat altered.) 



The margin of the umbrella is produced, in most cases but not in all, into a 

 horizontal shelf (vl.}, resembling the velum of the hydroid Medusa, but differing 

 from it in containing a series of branched vessels (end. lam'. ) continuous with the 

 canal-system and of course lined with endoderm. In the Hydrozoa, it will be 

 remembered, the velum is formed simply of a double layer of ectoderm with a 



