94 
CHARLES L. BOULENGER. 
the water taken in by the manubrium. These are pro- 
bably carried by currents caused by flagella on the endo- 
dermal epithelium to the narrow cavity of the proximal 
part of the manubrium, where they are acted on by the 
secretion of the gland-cells, and the disintegrated particles are 
then taken up by the cubical vacuolated cells which occur in 
this region. 
6. The Development of the Medusa-Buds. 
Gunther’s paper on the anatomy of Liinnocnida (1) con- 
tains a detailed account of the development of the asexual 
buds on the manubrium. His description of the process is 
briefly as follows : 
The young medusa makes its first appearance as a small 
outpushing of both layers of the manubrium. The apical 
ectoderm of this bud next boldly invaginates into the endo- 
derm and forms the hollow entocodon; the mouth of the 
apical invagination closes up and the wl^ole of the ento- 
codon becomes covered over by au overgrowth of ectoderm, 
and its cells become marked off from the cells of the peri- 
pheral ectoderm. At this stage the entocodon is a hollow 
sphere of ectoderm, one cell thick, enclosing a cavity which 
is really a portion of the exterior, which has been enclosed 
during the growth of the bud; meanwhile, owing to the 
invagination of such a comparatively bulky mass of ectoderm, 
the endoderm thins out so much as to be reduced to a single 
cup-shaped layer of cells enveloping the central entocodon. 
A second ingrowth of ectoderm now occurs. The ectoderm- 
cells at the apex of the bud grow down as a solid plug of 
cells into the apex of the entocodon, the effect of this second 
ingrowth of ectoderm being to push one wall of this organ 
into the other, with the result that the entocodon becomes a 
two-layered cup surrounding a plug of ectoderm cells ; the 
lumen of the entocodon may even disappear altogether, in 
which case it always reappears at a subsequent stage. Later, 
the endoderm cells surrounding the entocodon grow further 
