HTDEOZOA SCiPIIOMEDUS^E. 



251 



their umbrella, the gelatinous connective tissue of which is richly 

 developed and contains a quantity of strong fibrillae and a network 

 of elastic fibres, which structures confer upon it a greater firmness 

 and rigidity. 



Another characteristic of the group is derived from the structure 

 o" the edge of the umbrella. This is divided by a regular number 



RK 



FIG. 191. Aurelia aurlta, from the oral surface. MA, The four oral tentacles with the mouth 

 in the centre ; Gk, generative organs ; GH, aperture of sub-genital pit ; Rk, sense 

 organ (marginal body) ; EG, radial vessel ; T, tentacle at edge of the disc. 



of indentations usually into eight groups of lobes between which the 

 sense organs are contained in special pits (fig. 194). 



The marginal lobes of the Acalephse, like the continuous velum 

 of the Hydromedusce, appear to be secondary formations at the edge 

 of the disc. In the young stage known as Ephyra, which is common 

 at least to all the Discophora, they are present as eight pairs of 



Sars, "Ueber die Entwicklung der Medusa aurita und Cyanea capillata," 

 Archir.fiir Naturgescli, 1811. H. J. Clark, ' Prodromus of the History, etc., of 

 the Order Lucernaria" Journ. of Host. Soc. of Nat. Hut.. 1863. C. Claus, 

 " Studien iiber Polypen und Quallcn der Adria," Drnhxeliriften der It. 

 Academic der Wissensck. Wicn, 1877. C. Claus, ' Untersuchungen iiber 

 Charybdea marsupialis," Arleiten aus don Zoul. Imtltut, \\iun, 1878. Also 

 E. Haeckel, 1. c. 



