256 



GENERAL BIOLOGY 



Fig. 159. Scyphozoa. 

 A, Tessera princeps, order Stauromedusae. 



B, Periphylla hyacinthia, order Peromedusae. 



C, Charybdea marsupialis, order Cubomedusae. 

 G, gonads ; Gf, gastral filaments ; ov, gonads ; 

 Rf, annular groove ; Rk, marginal bodies ; Rm, 

 circular muscle; T. tentacles. (From Sedgwick, 

 after Haeckel.) 



Fig. 160. Examples of Alcyonoria. 

 Coral. A, Tubipora musica, organ-pipe 

 coral, a young colony. Hp, connecting hori- 

 zontal platforms ; p, skeletal tubes of the 

 zooids ; St, the basal stolon. B, Alcyonium 

 digitatum, with some zooids expanded. C, 

 Corallium, a branch of precious coral. P, 

 polyp. D, Pennatula sulcata, a sea-feather. 

 (A and B, from Cambridge Natural History; 

 C, from Sedgwick, after Lacaze Duthiers ; D, 

 from Sedgwick, after Kolliker). 



plant-conditions by their method of reproduction, namely, by fission and 

 budding, as well as often forming colonies. 



CLASSIFICATION 



There are three great classes of coelenterates - - Hydrozoa 

 ( ), Scyphozoa ( ), and An- 



thozoa ( ). 



The Hydrozoa possess neither stomodaeum nor mesenteries 

 ( ), and their sex-cells are discharged directly to 



the exterior. Hydra and Obelia belong to this class. 



The Scyphozoa may, or may not, possess a stomodaeum and mesen- 

 teries. The stomodaeum is more or less equivalent to the gullet in 

 coelenterates, serving as the passageway between mouth and the gas- 

 tro-vascular cavity or "stomach." The membranes which hold this 

 stomodaeum in place are called mesenteries. 



The position of tentacles and tentaculocysts is made use of in sepa- 

 rating the coelenterates into the various classes. 



Examples of Scyphozoa (Fig. 159) are: Tessera, order Stauro- 

 medusae; Periphylla, order Peromedusae; and Charybdea, order Cubo- 

 medusae. 



The Anthozoa are divided into two sub-classes as follows : Sub- 

 class I. Alcyonaria (Fig. 160), all of which have eight hollow, pinnate, 

 tentacles and eight complete mesenteries. They also possess one 

 siphonoglyphe, which is ventral in position, while all the retractor mus- 

 cles of the mesenteries lie on the side toward the siphonoglyphe 



( ). 



Examples of an Alcyonaria are the organ-pipe coral known as Tubi- 

 pora of the order Stolonifera, and the pretty sea-fans and the red coral 



