OF THE GENERATIVE ORGANS. 
421 
body, which on close examination was found to be simply a dilatation of the canal 
on which it was seated, having double walls continuous with 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 young individuals these 
canals are narrow and nearly equal throughout, 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 ciliee ; 
the outer membrane is dense, thinner, and much more transparent, figs. 16, I/. 
40. This account agrees in its general details very closely with that given by 
M. Milne-Edwards of the generative organs oi j^lquorea* ; and I regret the less not 
having been able to obtain male individuals, as he expressly states that in jEquorea 
the spermatozoa are developed in the same position. There is, however, one discre- 
pancy. M. Edwards states that the generative lamellse “ sont tout a fait distincts 
de la cavite digestive centrale.” I think that on repeating his examination he would 
find this not to be the case. In Oceania, at any rate, I could readily introduce a 
needle from the stomach into the canals, and show that the lamellse were mere dila- 
tations of their wall. 
In Polyxenia, where the canals are very short and the central cavity very large, the 
ova are situated in the under wall of the cavity, according to Will; but this author 
enters into no particulars as to the structure of the wall. 
41. The generative organs of the Phanerocarpse have been much investigated. 
The general result arrived at appears to be, that they are plaited tubular bands at- 
tached to the concave wall of a depression existing between the pillars of attachment 
of the stomachal membrane ; that they are altogether separate from the central 
cavity ; that the spermatozoa are developed in pyriform sacs opening externally, and 
that the ova lie free in the substance of the ovarial band. 
42. The structure of the generative organs in Phacellophora is as follows ; — The 
voluminous folded and plaited stomachal membrane is attached by four thick pillars 
to the under surface of the disc. The edges of the pillars are connected by a thin 
membrane, which is concave externally so as to form a sort of shallow depression or 
generative cavity, but the central and some of the marginal parts of this membrane 
are produced into long plaited processes, which hang far out of the cavity, fig. 18. 
Each process is a sort of sac communicating freely at its attached extremity with the 
cavity of the stomach, air, &c. passing readily from the one to the other It is in fact 
* Annales des Sciences Naturelles, t. xvi., quoted verhatim in Lesson's Histoire Naturelle des Zoophytes 
Acalephes. 
3 I 
MDCCCXLIX. 
