S6 



MANUAL OF ZOOLOGY. 



As regards the reproductive process in the Corynida, the 

 reproductive elements are developed in distinct buds or sacs, 



Fig 13 — Morphology of Corynida. a Fragment of Cordylophora lacustris, slightly 

 enlarged ; b Fragment of the same considerably enlarged, showing a polypite and 

 three gonophores in different stages of growth, the largest containing ova ; c Portion 

 oi Syttcoryne Sarsii yt\\h medusiform zooids budding from between the tentacles. 



which are external processes of the body-wall, and have been 

 aptly termed "gonophores" by Professor Allman. Strictly 

 speaking, Dr Allman understands by the term " gonophore " 

 only the ultimate generative zooid, that which immediately pro- 

 duces the generative elements. Great variations exist in the 

 form and development of these generative buds, and an exami- 

 nation of these leads us to some of the most singular pheno- 

 mena in the entire animal kingdom. In some species of 

 Hydractinia and Cory tie, the generative buds or "gonophores" 

 exist in their simplest form — namely, as sacciform protuber- 

 ances of the endoderm and ectoderm, enclosing a diverticulum 

 of the somatic cavity. In this form they are attached to the 

 " trophosome " by a short stalk, and they are termed " sporo- 

 sacs " (fig. 14, a). They are exactly hke the buds which we 

 have already seen to exist in the Hydra, with this difference, 

 that they are not themselves developed into fresh polypites, 

 but are simply receptacles in which the essential elements of 

 generation — the ova and spermatozoa — are prepared, by the 

 union of which the young Corynid is produced. 



In Cordylophora (fig. 13, ^) a further advance in structure is 

 perceptible. The gonophore now consists of a closed sac, 

 from the roof of which depends a hollow process or peduncle 

 — the " manubrium" — ^which gives off a system of tubes which 

 run in the walls of the sac. For reasons which will be imme- 

 diately evident, the gonophore in this case' is said to have a 

 " disguised" medusoid structure (fig. 14, V). 



