122 



COMPARATIVE ANATOMY, 



§ 06. 



In those Medusae which have no longer any relation to Hydroids, 

 the generative matters are formed in the wall of the gastro- 

 vascular system, just as in the Medusas of the Hydroid-Polyps, 

 and the Siphonophora. These matters are generally formed in the 

 radial canals (iEquoridas), or in the pouch-like diverticula of the 

 stomach (^Eginidas) . When the canals are narrow the genitals form 



freely projecting diverti- 

 cula, which, when much de- 

 veloped, may have the form 

 of ruff-like folds. The 

 radial canals form lamellar 

 enlargements intheGeryo- 

 nida?, when the generative 

 matters are developed. In 

 all forms the lower wall 

 of the canal, or that placed 

 away from the umbrella, 

 forms the genital region 

 (Fig. 85, g). The germinal 

 matters in some cases reach 

 the exterior through the 

 stomach, and in other cases 

 by a rupture of the tissue. 

 In the Discophora the 

 rgans have 

 always much the same re- 

 lations, and differ but little 

 in position and form. They 

 consist of four or eio-ht 

 frills, curved in a semi- 

 lunar form, and arranged 

 in a rosette on the inner 

 surface of the umbrella 

 (cf. supra, Fig. 44, ov) ; 

 the frills are formed by diverticula of the gastrovascular system. 

 They are placed in depressions on the lower surface of the disc, 

 or hang freely down from it, often in numerous folds. 



The Lucernarias have the generative organs in the form of eight 

 radially-arranged longitudinal ridges, placed on that part of the 

 body which corresponds to the sub-umbrella of the Medusas, where 

 they form projections into the pouches of the gastrovascular system. 

 They represent, therefore, an intermediate form between the Hydro- 

 medusas and Discophora. 



Fig. 49. Diagram of a radial vertical section 

 through a sexually mature Geryonid (Carmariua 

 hastata) ; on the right it is taken through the 

 whole length of a radial canal, and on the left 

 through the lateral wings of a genital lamella, at 

 an interradial plane, b Marginal vesicles, c Cir- 

 cular vessel, g Generative products, h Clasp of 

 the mantle, h Stomach. I Gelatinous umbrella. 

 p Stomachal stalk, r Eadial canal, s I Its inner ; 

 r s Its outer wall, u 1c Cartilaginous ring, v Ve- 

 lum. Z Tongue-like process (after E. Hackel). 



generative 



