MEDUSA. 19 
longitudinal canal-like tubes, which run along the stomach, are probably the four 
corners of an ordinary quadrilateral stomach which has become nearly blocked up 
owing to the growth of the gonads. Ido not think that they are permanent canals, 
like the radial canals, but rather spaces in the stomach which have not become filled up 
with endoderm. At the same time it is possible that they might be used as channels 
for the conveyance of nutriment to the developing gonads. 
Although the gonads have every appearance of being next to the endoderm, 
without the intervention of a layer of mesoglea, and without a trace of ectoderm, still 
there is no evidence that they are of endodermal origin. The gonads are shut off from 
the endoderm by a very thin delicate membrane which may be a layer of mesoglea. 
As the gonads are fully ripe they have probably in the course of development absorbed 
all the adjacent ectoderm cells. The position of the ripe gonads is certainly peculiar, 
and a few young and intermediate stages were much wanted for tracing the 
development. 
The sections of the stomach belonging to the specimen which has shed all its 
gonads are also of interest. The positions of the shed gonads are marked out by 
spaces, which are either straight simple cavities or tubular cavities more or less curved 
(fig. 5). These cavities are lined with a well-marked ectoderm which has apparently 
developed after the shedding of the gonads. The new ectoderm is continuous with the 
old ectoderm on the outside of the stomach. 
The specimen which has quadrangular holes alongside the perradial ridges has 
somewhat the appearance of having its gonads arranged in short, transverse folds, as 
described in the other species of the genus. But it is after all only an external 
resemblance. 
The four perradial canals are in direct communication with the stomach through 
the interior of the ‘‘mesenteries” upon which the stomach is suspended, and which 
form its cruciform base. The four interradial canals have no direct communication 
with the stomach. They run nearly the whole length of the sub-umbrellar cavity. 
Some terminate at their proximal end, ie., nearest to the top of the umbrellar 
cavity, either in a straight point, or in slight diverticula (fig. 2), without any 
communication with the stomach or the perradial canals. In this condition they 
have every resemblance to long centripetal canals which develop direct from the 
circular canal. 
A few of the interradial canals at their proximal ends do communicate with the 
perradial canals by means of irregular branches. There is either a single branch 
running to one of the adjacent perradial canals, or two opposite branches running to 
both the adjacent canals. The union with the perradial canals is at the point where 
the “mesenteries ” are about to becomes radial canals. In one specimen none of the 
interradial canals show any connection with the perradial canals. But in another 
specimen three of the interradial canals have a connection by means of an irregular 
branch or branches. 
VOL, V. Y 
