106 
CHARLES L. BOULENGER. 
and contain large, colourless and highly refringent granules of this 
substance. 
Fig. 6. — Longitudinal section of the proximal region of the manu- 
brium. Here the endoderm forms a low epithelium, with gland-cells 
(gl. c.), and vacuolated cells, containing food-balls (/. i.) 
Fig. 7. — Transverse section of a young medusa-bud just after the 
formation of the entocodon by invagination. The latter ( ent .) is almost 
square and at its four corners constricts the double cup of endoderm 
interradially (int. end.). This leads to the formation of four per- 
radial pouches of endoderm (end. p.), from which the radial canals of 
the adult are derived. 
Fig. 8. — Longitudinal section through an old medusa-bud. The 
velum ( vel .) is already perforated, and the manubrium (man.) projects 
as a rounded boss into the umbrella cavity. Three of the four perradial 
tentacles are shown (tent. per.). Note that the manubrial endoderm is 
already differentiated from that of the rest of the gastric cavity ; it is 
always indicated at this stage, even if the manubrium itself has not yet 
been evaginated. 
