THE HYDROPHORA. 



119 



termed nematophores by Mr. Busk/ In Ophiocles (Hincks) 

 they are tentaculiform. 



It frequently happens that the gonophores are developed 

 upon special stalks, each of which has essentially the struct- 



FiG. W.—Campanularia (after GoEcnhatir).— ^, Hydraiith : e, its peduncle ; c', hy- 

 drorlieca ; o, mouih; /(?. tentacles; A;'. dii,'estive cavity, continuous with the bo- 

 matic cavity k, contained in the peduncle and in the creeping t-tem, *S'. li, gonan- 



fium containing two medusiform Z(6id^■ or gonophores w ; the somatic cavity 

 '' is in connection with that ol" the creeping stem. C, Bud. 



ure of a mouthless hydranth. This is termed a hlastostyle. 

 In some blastostyles (Fig. 15), during the development of the 

 buds of the gonophores, the ectoderm splits into two layers — 

 an inner, which invests the central axis formed by the endoderm 

 with the contained prolongation of the somatic cavity ; and 

 an outer, chiefly, if not wholly, chitinous layer. Into the in- 

 terspace betw^een these two, the budding gonophores project, 

 and may emerge from the summit of the gonaiigium^ thus 

 formed, either to develop the reproductive elements, and shed 

 them while still attached, or to be set at liberty as free medu- 

 soids (Fig. 16). 



Alhnan ^ has shown that, in Dicoryne conferta^ the gono- 



^ They are described under the name of " clavate ororans," antl compared 

 with the tentacles of Dipln/dce \n my memoir on the "4-ffinities of the Medu- 

 sa'." ("Philosophical Transactions," 1849.) 



2 " Monograph of the Gymnoblastic, or Tubularian Hydroids," 1871, p. 31. 

 In this beautifully illustrated and elaborate work, the student will find, not 

 6 



