154 



COELENTERATA. 



the pneumatocyst, and contains a central tube putting the cavity 

 of the pneumatocyst in communication with the exterior. It is 

 placed on one side of the pneumatophore, and its central tube 

 (pistillum) is surrounded by a number of radial chambers, which 

 are separated by septa and communicate with the pericystic (endo- 

 dermal) space of the pneumatophore. Very possibly the aurophore 

 is a gas-secreting gland. 



Fain. 1. Stephalidae. Stcplialia H. ; Stcplionalia H. 

 Fam. 2. Rhodalidae. Auralia H. ; Rhodalia H. 



a 



A-ph 



Fir;. 120. Stephalia corona (after Haeckel). a, side view ; b, section. Aph Aurophore ; 

 Sg corona of nectocalyces ; P siphons with their tentacles ; CP the large central siphon, 

 the enteron of which forms the central tube of the siphosome (coenosome or stem). 



Section 4. CYSTONECTAE. PHYSALIDAE. 



Siphonantliae with a large apical pneumatophore without necto- 

 calyces and without bracts. Pneumatocyst with an apical stiijma. 



This order includes Physalia, the well-known Portuguese Man 

 of War, which we may take as type. 



Physalia possesses a large pneumatophore lying nearly horizontally 

 and bearing posteriorly and ventrally the numerous siphons, palpons, 

 and branched gonostyles. The stigma is at the front end of the 

 pneumatophore, and leads into a large pneumatocyst. The pericystic 

 cavity is simple and not divided. The air-secreting cells or pneu- 



