23 
The medusæ-buds are found in all stages and sizes; the 
largest ones show clearly that they will be set free as real medusæ. 
Already tiny buds, of 0,160 mra. in diameter, have distinet rudi¬ 
ments of two marginal tentacles; in larger buds these have quite a 
considerable size but are still clumsy; nevertheless the tentacles 
are easily overlooked in many of the largest buds, because they 
have been bent up and concealed inside the umbrella. In the latter 
case the medusæ-buds appear elongated, fusiform (PI. I, Fig. 2 mé) 
and at first sight do not resemble medusæ at all; in clearing witli 
glycerine or xylol etc. the marginal tentacles and the other rnedu- 
soid structures are easily observed. There is a 
short manubrium ; no mouth is yet formed, neither 
are there any indications of mouth-tentacles. In 
transverse sections the cavity of the manubrium 
is quadrangular; a narrow canal connects it 
with the gastric cavity of the mother-polype. 
The umbrella contains four distinet, wide and 
simple radial canals, connected distally by a 
ring-vessel; a velum is indicated as an outgrowtli 
from the ectoderm of the subumbrella. 
The exumbrellar ectoderm contains numerous 
large nematocysts (ca. 0,004 mm. in diameter), 
most of them arranged as a broad band across 
the bell; this band may be distinctly seen already in quite young 
buds. The tentacles originate opposite the distal ends of two radial 
canals; they are hollow, their cavity connected with the ring- and 
radial vessel; no pigmented eye-spot is seen at their base. Between 
the tentacles the margin of the bell shows a small projecting fold 
at the ends of the other two radial canals, possibly indications of 
a new pair of tentacles, developing after the liberation of the me- 
dusa. Even in the most developed stage observed the tentacles 
appear clumsy, finger-shaped, somewhat shorter than the bell (Fig. 3). 
Sometimes they are bent in the way shown in textfigure 6; in this 
case they may be mistaken as going to branch into a group of two. 
Fig. 6. Ichthyoco- 
dium sarcotretis. 
Medusa bud. 
m : manubrium; 
r : marginal ten- 
tacle. 
