1 8 ON THE ANATOMY OF THE FAMILY OF THE MEDUSA 



arranged round their hemispherical extremities. As the individual I 

 observed was a )-oung one (the generative organs not being 

 developed), I conclude that these were young forms of the longer 

 tentacles, fig. 36. 



37. Of the Generative Organs. — It has been already noticed with 

 regard to the CryptocarpEE by Will (in Geryonia, Thauniantias, Cytceis, 

 Polyxenta), and by Milne-Edwards (in Aiquorea), that the generative 

 organs are connected with some part of the system of canals, but they 

 do not attempt to define the nature of this connection. I shall en- 

 deavour to do this, and to show that the generative organs, both in 

 these and in the Phanerocarpas and Rhizostomidae, are always portions 

 more or less developed of the wall of this .system ; and therefore con- 

 sist of the two " foundation membranes," in or between which the 

 generative elements, whether ova or spermatozoa, are developed. 



38. In Thamnantias there are four canals radiating from the centre 

 of the disc, at right angles to one another, and terminating in a circular 

 vessel at the edge of the disc. Near its termination each has a rounded 

 body seated upon it. In most of the specimens I examined this body 

 was distended with ova, and its structure was thereby obscured ; but 

 in one instance it was replaced by an elongated, somewhat pyriform 

 body, which on close examination was found to be simply a dilatation 

 of the canal on which it was seated, having double walls continuous 

 "tt'ith those of the canal, only much-thickened, and a central cavity 

 communicating freely with that of the canal. This was without 

 doubt a young generative organ, fig. 4. 



39. In Oceania the canals are very numerous, and radiate from the 

 wide central cavity to the circular vessel at the margin of the disc. In 

 ypung individuals these canals are narrow and nearly equal through- 

 out, but in adults their inferior wall, for the middle three-fifths of their 

 extent, is greatly enlarged and hangs down in folds or plaits, fig. 15. 

 Under the microscope the wall exhibits an immense number of ova, of 

 all sizes and stages of growth, lying in its substance ; and if the edge 

 of a fold be examined, these are seen to be placed between the inner 

 and outer membranes. The inner membrane is thick, and composed 

 of projecting cells with very long ciliae ; the outer membrane is dense,, 

 thinner, and much more transparent, figs. 16, 17. 



40. This account agrees in its general details very closely with that 

 given by M. Milne-Edwards of the generative organs oi y^qiiorea^ \ 

 and I regret the less not having been able to obtain male individuals,, 

 as he expressly states that in Aiquorea the spermatozoa are developed 



' Annales des Sciences Natiirelles, t. xvi., quoted vcrhatiin in Lesson's Histoire Naturelle 

 des Zoophytes Acalephes. 



