398 REPORT— 1863. 
circle round the summit of this primordial bud. These, however, do not 
show themselves as free processes ; for, simultaneously with their appearance, 
the ectoderm of the summit of the bud becomes split into two layers (a’, a’’), 
which become more and more widely separated from one another as the pro- 
cesses continue to elongate, the outer layer arching over the space which is 
surrounded by the four processes. During this elongation, the ectoderm which 
occupies the four intervals between the roots of the processes is carried 
upwards as a continuous membrane, stretching across from one process to 
another in the manner of a web. 
The result of this is, that we have now the distal portion of the bud in the 
form of a deep cup formed of ectoderm, closed over by a layer also consist- 
ing of ectoderm, and having its walls traversed by four equidistant czcal 
tubes, whose cavity is continuous with the original cavity of the bud, and 
which are lined by a continuation of the endoderm of the bud. There is no 
Fig. 16.—Development of medusa in Corymorpha nutans. 
om 
SRdrcomeuenn tench 
Rae 
A, medusa somewhat more advanced than E in fig.15; the bulbous terminations of the 
gastrovascular canals have coalesced, and one of them has become projected into a. long 
thick tentacle. B, medusa just after liberation from the trophosome. 
difficulty in recognizing in these tubes the radiating canals of the future 
medusa, and in the web of ectoderm which unites them the umbrella. 
From the central point of the area included between the bases of the four 
canals another hernial process (fig. 15 C d and D d) has already begun to make 
its appearance, composed of ectoderm and endoderm, and containing a pro- 
longation of the original bud-cavity. It advances as a thick process in the 
axis of the cup, and is at once recognizable as the future manubrium, 
