278 R. T. GUNTHER. 
which is capable of giving rise to buds forms a zone completely 
surrounding the manubrium and covering about two thirds of 
the surface of that organ, leaving a distal zone free from buds, 
as in Sarsia. Thus the area on which Medusa buds may 
develop is approximately co-extensive with the germinal area 
on which the reproductive elements may arise in sexual in- 
dividuals. 
The ectoderm cells of the gemmiferous region of the manu- 
brium are much vacuolated ; their nuclei for the most part lie 
deeply, close to the endoderm, but some have a more super- 
ficial position between the vacuoles. Cell boundaries are 
either altogether absent or could not be demonstrated. The 
cells of the endoderm of this region are arranged in several 
layers; in character they are polygonal, very granular, and 
provided with definite walls. The mesoglea, which is nowhere 
very thick, disappears altogether beneath the larger buds. It 
is thickest in the distal third of the manubrium, in the region 
which does not give rise to either medusa buds or generative 
products. 
The young bud first makes its appearance as a small local 
outpushing of the wall of the manubrium. This outpushing 
(figs. 8 and 8 a) affects all the cell layers and is hollow, its 
cavity being a diverticulum of the gastric cavity of the parent. 
Thus a part of the digestive epithelium of the parent becomes 
the endoderm of the young bud, and it is not unlikely that by 
means of this endoderm the bud may obtain the nutriment for 
its further growth by the direct absorption of such food matter 
as may enter its own “stomach” from the gastric cavity of 
the parent. 
The young bud does not remain long in this stage. A change 
soon appears to come over the ectodermal cells at the apex of 
the bud. Their protoplasm instead of being vacuolated be- 
comes dense and more granular than before, while the cells 
themselves become somewhat thicker, and their nuclei take up 
their position in an even row next the endoderm. These 
changes foreshadow the next step. The apical ectoderm bodily 
invaginates into the endoderm (figs. 9 and 9a) at the tip of the 
