E. W. BERGER ON THE CUBOMEDUS. 75 
Charybdea they lie wholly enclosed within canals of the supporting 
lamella (Fig. 32, upper part). They run longitudinally, and near the 
base of each tentacle pass out of their canals and become strictly 
subectodermal (Figs. 31, 32). This is for Charybdea. In Tripedalia 
they rarely come to lie in closed canals as in Charybdea. These 
facts show beyond doubt that these muscles are developed from the 
ectoderm. Claus has suggested their ectodermal origin, but did not 
demonstrate it. He also suggested that they become inclosed in 
canals by the supporting lamella pushing up around them and finally 
fusing above them. This, I believe, is demonstrated by the conditions 
in Tripedalia (Fig. 29). Here the canals usually remain open, but 
occasionally, as in the left-hand canal, one may become completely 
inclosed. This condition of things suggests the intra-lamellar muscles 
found in actiniarians. The nuclei found in the canals with the muscle- 
fibers probably belong to the cells from which the muscles become 
differentiated. Claus figures these muscle-fibers and nuclei, and it may 
be added that the supporting lamella he figures, for C. marsupialis, 
is much thicker than I have figured it for C. Xaymacana and 
Tripedalia cystophora. The number of muscle-canals also is greater 
and occupies a much greater depth of the thickness of the lamella. 
Since Claus gives a figure of a transverse section showing the muscles 
in their enclosed canals, I have not deemed it necessary to duplicate 
his figure. In the transition from a tentacle to a pedalium, the 
muscles are most strongly developed toward and at the edges of the 
pedalium. This is true for the pedalia in general, and accounts for 
the readiness with which they can be bent inwards, as noted in the 
physiological part of this paper. 
(c) I have found a single ganglion-cell among the cells of the 
ectoderm of the tentacles. This showed so plainly that I have figured 
it (Fig. 28). Other ganglion-cells no doubt exist, but could probably 
not be distinguished from other cells. In its position in Fig. 28 it 
appears to be associated with the nettle-cell shown just above it. Its 
position is very much the same as that figured by Lendenfeld (25a). 
The Endoderm—The cells of the endoderm of a tentacle are 
long and quite slender (Fig. 31). At their bases they are vacuolated 
quite like the cells of the ampulla and the canal of the sensory 
clubs. They contain a well-formed nucleus with a nucleolus. In 
their distal half small light bodies with a dark center are very 
evident. These bodies are evidently a secretion. 
