40 Coelenterata. 



differentiation the production of the highly characteristic accessory leaves 



leads to Struthiopteron , while by reduction of the leaves to the dorsal 

 clusters of zooids Sarcophyllum arose. 



Balss gives a systematic account of the Pennatulids, based largely on 

 material from Japan. He points out that their form is correlated with the con- 

 ditions under which they live. Those in shallow water have either no axis or 

 only a small and thin one (Renilla, Pennatula), intake of water leading to 

 turgidity and stiffening of the colony, and quick expulsion of water, bringing 

 about great contraction, afford means of rapid adjustment to the calm or agi- 

 tated condition of the water. Genera from 200-300 m. (Protoptilum, Distichop- 

 tilum) and most Spicatse are smaller, 20 to 30 cm. long, and their polyps are 

 not arranged in leaves but are directly sessile on the rachis, so that the whole 

 colony is rod-like and fixed in the mud at the sea-bottom. From greater depths 

 there are two types - - (1) very long colonies Balticina, Funiculina, Hali- 

 pteris - - with small polyps on both sides of the long rachis, and with an elastic 

 axis traversing the whole length of the colony; (2) the true deep sea genera 

 like Umbellula, Chunella, Scleroptilum and Anthoptilum, with large polyps 

 either in a terminal cluster or on both sides of the rachis (but not in trans- 

 verse series). The significance of the large size of the polyps is not clear. The 

 littoral genera are all highly differentiated; no member of the primitive group 



the Spicatse has a littoral habit. The author comments on the com- 

 parative value of certain characters which have been used in diagnosis, on the 

 influence of temperature and on the geographical distribution. He describes 

 Kophobelemnon 1, Sclerobelemnon 2, Funic. 1, Stachyptilum 1, Echinoptilum 1, 

 Virgularia 3 (the absence of sarcosome from the end of some specimens is pro- 

 bably due to the attacks of Gastropods, the leaves of this genus have no spi- 

 cules and are thus unprotected against attack), Scytalium 1, Balticina (pro 

 Pavonaria) 1, Pennatula 4, Pteroides 4 (1 n., which is a link between Pt., Gode- 

 froya and Sarcophyllum}, Calibelemnon 2, Lituaria 2 (In., which breaks down 

 the limits between L. and Clavella), Cavernularia 4 (1 n.). The canal system 

 of Calibel. indicum is described; of the 4 longitudinal canals the dorsal and 

 ventral are larger; into the upper part of the dorsal canal opens the dorsal 

 siphonozooid, into the ventral canal the large terminal polyp. There are, 

 parallel to the lateral canals of the rachis, two accessory canals into which 

 open the lateral polyps and siphonozooids. The latter are rudimentary, con- 

 sisting of stomoda3um only. The accessory canals open into the 4 main canals 

 and into other canals enveloped by muscles. In this species the terminal polyp 

 and terminal zooid persist. 



Broch( 1 ) describes Virgularia n. sp. (juv.) from Liideritzbucht, which is pro- 

 bably identical with the South African examples referred by Hickson to rein- 

 wardti. 



Brochf 2 ) advocates the use of the nature and arrangement of the spicules as 

 systematic characters in the Pennatulids, and describes Pteroeides 1 and Sarco- 

 phyllum 1 n. from Western Australia. - See Broch( 3 ). 



Kiikenthal( 4 ) describes from the collections of the German Deep-Sea Expe- 

 dition Pennatula 4 (1 n. and 1 n. var.), Virgularia 1 n., Funiculina 2, Protop- 

 tilum 1 n., Anthoptilum 1, Scleroptilon 1, Kophobelemnon 1 n., Actinoptilon n. 

 (a transitional form between the radial and bilateral Pennatulids, nearly related 

 to Lituaria} 2, Veretillum 1. 



C. Hydrocorallia. 



For Stylaster see Thomson ( { ), for the phylogeny, supra p 8, Kemna. 



