74. JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 
like those I describe for the endothelial cells of the tentacles (see 
below), and that they aid in the formation of the floating cells. I 
thought I saw such buds just at the entrance of the lumen of the 
peduncle into the ampulla, but could not find conclusive evidence. 
The Tentacles and the Pedalia.—My observations on the tentacles 
were begun with the object of demonstrating a flagellate mechanism 
similar to the one described above for the endothelium of the 
peduncle. While I have failed to demonstrate such a mechanism for 
the tentacles, yet several interesting points came to my notice. It 
will be remembered that the tentacles of the Cubomedusze are not 
directly attached to the bell, but that a blade-like portion, the 
pedalium, intervenes between the tentacles and the bell. For figures 
of the pedala and the tentacles the works of Haake, Claus, Conant 
and Maas”? may be consulted. 
The Ectoderm.—The ectoderm of the tentacles is the seat of a 
number of differentiations. It is quite thick, as the figures (28 and 
29) show, and in this respect is very different from the pedalia, on 
which the ectoderm cells are quite cubical. I found evidence of cilia 
here and there, but I can add nothing definite about them. Neither 
can Il add any definite statements regarding the ectoderm cells proper, 
but what I have to say relates to their differentiations. 
(a) The thread cells are of two kinds, larger ones and smaller 
ones. This is well shown in Fig. 29, which is part of a transverse 
section of a tentacle of Tripedalia. Two kinds of nettle-cells are also 
present in the tentacles of Charybdea, but they were specially well 
shown in Tripedaha. The structure of these thread-cells seems to be 
typical, and I have little more to say about them. I wish, however, 
to call attention to the five or six unstriped muscle-fibers that are 
attached to their basal lateral parts, and which connect them with 
the basement membrane (Figs. 28, 29). Claus describes these muscle- 
fibers and mentions that Fr. Muller has described them before him, 
but I have not found them mentioned elsewhere in the literature of 
nettle-cells. Professor Brooks tells me, however, that he has often 
found them. It would appear from Fig. 29 that they serve to retract 
the thread-cells from the surface. Claus suggests that the muscles 
are developed from the cnidoblasts. 
(b) The plain subectodermal muscle-fibers are of interest. In 
