ON MQ@RISIA LYONSI. 367 
mens, and examination shows this to be due to the formation 
of four deep longitudinal pouches (fig. 3) situated per-radially 
and giving this part of the manubrium the form of a cross 
when viewed from above or below. 
From the top of the pouches four radial canals are given off 
which traverse the umbrella and terminate on the margin 
where their cavities become continuous with the cavity of the 
circular canal. These canals are lined by a very low epithe- 
lium consisting of very small, clear, cubical cells continuous 
with similar though slightly larger cells which cover the ex- 
umbrellar wall of the stomach. 
The gonads are to be found on the walls of the stomach ; 
the generative cells are distributed over the whole of the 
ectoderm of this region of the digestive sac, and attain their 
greatest thickness in the concavities between the per-radial 
pouches. . 
When we examine an adult medusa we find that the 
stomach has increased in size and has changed considerably in 
shape. The four per-radial pouches have become drawn out 
into long finger-shaped diverticula which extend more than 
half-way down the sub-umbrella (fig. 4). 
Except at the distal extremities, the cavities of these 
diverticula are continuous with the cavities of the radial 
canals. 
‘The gonads extend onto the walls of the diverticula and 
attain at this point a considerable thickness. 
In the adult medusa we thus find an arrangement of the 
gastro-vascular system very similar to that described by 
Browne (6) in Willsia; as in that genus the study of imma- 
- ture forms proves the gonadial diverticula to be parts of the 
stomach. Sections (fig. 10) show that the outer or ex- 
umbrella walls of the diverticula are lined by small endo- 
derm cells identical in all respects with those in the radial 
canals, whereas the remainder of the lining is formed by 
larger and taller cells directly continuous with and merging 
into the endoderm cells at the base of the stomach. 
All the specimens examined by me were of the male sex ; 
