MANUAL OF ZOOLOGY. 



In all the Calycophoridce the coenosarc is filiform, cylindrical, 

 imbranched, and highly contractile, this last property being due 

 to the presence of abundant muscular fibres. " The proximal 

 end of the coenosarc dilates a little, and becomes ciliated in- 

 ternally, forming a small chamber" which communicates with 

 the nectocalycine canals. " At its upper end this chamber is 

 a little constricted, and so passes, by a more or less narrowed 

 channel, into a variously-shaped sac, whose walls are directly 

 continuous with its own, and which will henceforward be termed 

 the somatocy'st (fig. 27, 3 b). The endoderm of this sac is cili- 

 ated, and it is generally so immensely vacuolated as almost to 



Fig. 27. Morphology of the Oceanic Hydrozoa. i. Diagram of the proximal ex- 

 tremity of a Physophorid. a Pneumatocyst. 2. Vo%tia pentacantha, one of the 

 Calycophoridee. n Nectpcalyces ; p Polypites ; t Tentacles. 3. Diagram of a 

 Calycophorid. _ a a' Proximal and distal nectocalyces ; b Somatpcyst ; c Coenosarc ; 

 d Hydrophyllium or bract ; e Medusiform gonophore ; / Polypite. The dark lines 

 in figs, i and 3 indicate the endoderm, the lig 



the ectoderm. (After Huxley.) 



ight line with the clear space indicates 



obliterate the internal cavity, and give the organ the appearance 

 of a cellular mass " (Huxley). The polypites in the Calyco- 

 fhorida often show a well-marked division into three portions, 

 termed respectively the proximal, median, and distal divisions. 

 Of these, the " proximal" division is somewhat contracted, and 

 forms a species of peduncle, which often carries appendages. 

 The " median " portion is the widest, and may be termed the 

 " gastric division," as in it the process of digestion is carried 

 on. It is usually separated from the proximal division by a 

 valvular inflection of the endoderm, which is known as the 

 "pyloric valve." The polypites have only one tentacle " de- 



