98 MANUAL OF ZOOLOGY. 



tubes, of a straw colour, and not unlike straws to look at ; hence 

 the common name of pipe-coralline given to this zoophyte. 

 Each tube is filled with a soft, semi-fluid, reddish ccenosarc, 

 and gives exit at its distal extremity to a single polypite. The 

 polypites are bright red in colour, and are not retractile within 

 their tubes, the horny polypary extending only to their bases. 

 The polypites are somewhat conical in shape, the mouth being 

 placed at the apex of the cone, and they are furnished with 

 two sets of tentacles. One set consists of numerous short 

 tentacles placed directly round the mouth ; the other is com- 

 posed of from thirty to forty tentacles of much greater length, 

 arising from the polypite about its middle or near the base. 

 Near the insertion of these tentacles the generative buds are 

 produced at proper seasons. The generative buds remain 

 permanently attached, but each is furnished with a swimming- 

 bell, in which canals are present. The manubrium is destitute 

 of a mouth, and " the swimming-bell is converted into a 

 nursery in which the embryo passes through the later stages 

 of its development" (Hincks). 



Coryomorpha nutans maybe taken to represent those Cory- 

 nida in which there is no polypary and the hydrosoma is simple. 

 It is about four inches in length, and is fixed by filamentous 

 roots to the sands at the bottom of the sea. It consists of a 

 single whitish polypite, striped with pink, and terminating 

 upwards in a spear-shaped head, round the thickest part of 

 which is a circlet of from forty to fifty long white tentacles. 

 Above these comes a series of long branching gonoblastidia. 

 bearing gonophores, and succeeded by a second shorter set of 

 tentacles which surround the mouth. The gonophores become 

 ultimately detached as free-swimming medusoids. 



Another remarkable example of the Corynida is Hydractinia 

 (fig. 23). In this genus the polypites are gregarious, and the 

 polypary forms a horny crust which spreads over shells and 

 other foreign bodies. The tentacles of the nutritive zooids 

 form a single sub-alternate series. The generative buds are 

 produced upon imperfect, non-tentaculate polypites ; and are 

 mere sac-shaped protuberances, enclosing diverticula from the 

 body-cavity, but not detached from the parent organism. 



ORDER III. SERTULARIDA (Thecaphora, Hincks). This 

 order comprises those Hydrozoa " whose hydrosoma is fixed by 

 a hydrorhiza, and consists of several polypites, protected by hydro- 

 thecce, and connected by a ccenosarc, which is usually branched and 

 invested by a very firm outer layer. Reproductive organs in the 

 form of gonophores arising from the ccenosarc or from gonoblas- 

 tidia" (Greene). 



