432 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
very wide velum, figure G, is pushed out to form eight hemispherical 
pouches, four of them radial and four interradial, in the planes of 
the eight tentacles. They project so much that they are prominent 
in profile view, as shown in figure H. May they not be homologous 
with the pouches that become converted into marginal vesicles in the 
vesieulated medusae ? 
‘‘The adult medusa is shown in figs. /, J and K. When it is swim¬ 
ming np from the bottom the tentacles are carried tightly curled up 
close to the edge of the bell. When it reaches the surface they are 
suddenly extended on all sides, shown in fig. K. They are nearly 
straight, but their tips are a little bent and sometimes coiled. This 
attitude is preserved only for a few seconds and the medusa at once 
begins to sink towards the bottom, while the tentacles coil up at their 
tips and assume the position shown in fig. I. The bell also becomes 
flattened and nearly hemispherical, and before the animal reaches 
the bottom of the aquarium it usually assumes the appearance which 
is shown in fig. J . As it nears the bottom it suddenly draws in its tenta- • 
cles and rises to the surface, and again extends them, as shown in fig. 
K .... The figures of the adult medusae, I, J, K , are much less magni¬ 
fied than the others, which are all drawn to the same scale.” 
The memoir of 1886 also contains an account, (p. 391), of a planula 
that was reared from the egg of Turritopsis, and of the larval or first 
liydranth which arises from the planula and forms the basis of a new 
hydroid cormus. These stages are shown in figures 2 and 3 of plate 
42. A record is also made (p. 391) of the fact that the planula does 
not become converted into a liydranth, but becomes a root, from 
which the first hydranth is formed as a bud. 
Dr. S. Rittenhouse has recently reared a number of planulae of 
Turritopsis from the egg, and he has verified the observation that the 
planula becomes a root, from which the first liydranth arises as a bud, 
and he has traced the further development of the liydranth. When 
joined to the memoir of 1886, his observations, which are contained 
in Part 3 of this paper, give us all the prominent facts in the life his¬ 
tory of Turritopsis. 
