THE DISCOPHORES, OR LARGE MEDUSAS. 
121 
acceleration of their movements, that they are attempting to 
escape.” 
From the centre of the lower or concave surface of the disc — 
the top of the domed cavity — is suspended the digestive sac, a 
somewhat four-sided, proboscis-like body, terminating in a 
quadrangular mouth, which we readily recognise as a polypite, 
in spite of its disguise in the adaptive dress that fits it for a 
locomotive existence. The angles of this mouth are extended 
into lobate processes, often of very considerable length (Plate 
LXX. fig. 10), which are hung with fringes and furbelows, and 
form a striking feature of the organism, projecting as they often 
do far beyond the opening of the swimming-bell. These ap- 
pendages, which have been styled the 66 grasping arms,” assist in 
securing the prey and conveying it to the mouth. They also in 
some cases subserve another and very different purpose ; within 
their ample folds, marsupial pouches are, as it were, extempo- 
rised, in which the ova pass through certain stages of their 
development, and ripen into the perfect embryo. At its upper 
extremity the pendent digestive sac opens into a somewhat 
extensive cavity, from which a certain number of tubular pro- 
longations are given off, which penetrate the substance of the 
disc, and, after dividing, and in some cases sub-dividing, and 
anastomosing, so as to form a complicated vascular network, 
terminate in a circular canal that runs round the disc a little 
within the margin. Through these tubular offshoots of the 
stomach, radiating through the inferior stratum of the swim- 
ming-bell, its contents are at once distributed, and applied to 
the nutrition of the whole structure. They compare with the 
central channel, traversing all the ramifications of the common 
flesh in the plant-like zoophyte, and communicating directly 
with the stomachs of its multitudinous hydrse, by which the 
prepared pabulum is conveyed throughout the length and 
breadth of its complex organism. 
In close connection with the central cavity, just described as 
surmounting the digestive sac, and also with the radiating tubes 
concerned in the circulation, are found certain pouches within 
which the ovary and spermary are lodged. These pouches open 
into the body-cavity, and the ova pass into it in due time, and 
find their way through the mouth to the marsupia prepared for 
their reception during the further stages of their development. 
The deeply-coloured reproductive organs show distinctly through 
the transparent disc, and give rise to the cruciform figure which 
adorns the summit. So much may suffice in the way of struc- 
tural detail. We have now the grand features of this organic 
type clearly before us.* It is less easy to describe the various 
* I have not referred to the partially developed membranous veil which 
in some species surrounds the margin of the disc, nor to the curious internal 
