Ne. 1. ] ACTINIARIA OF THE BAHAMAS. 53 
against it. Von Heider’s idea, that it is due to a special secre- 
tion produced by the ectodermal cells, seems much more in 
accordance with the histological structure. I was inclined at 
first to consider the pyriform cells the producers of the secre- 
tion, but am now undecided as to whether they are not really 
nerve ganglion cells. They occupy the position of the nerve 
layer of other parts of the body, and their slight development 
in some species seems to indicate that they are not directly con- 
cerned in producing the adherence of foreign bodies. I regret 
that I was unable to study maceration preparations of fresh 
specimens, from which, no doubt, this point might be settled ; 
and it would be exceedingly interesting, in connection with the 
physiology of secretion, to make such observations, and deter- 
mine the existence or non-existence of nerve cells in the 
verruce. 
The mesogloea of the column wall is rather thick (Pl. IV., 
Fig. 7), and is raised into numerous obtuse elevations. The 
endoderm is as usual abundantly supplied with “yellow cells.” 
There is no special sphincter muscle distinct from the ordinary 
endodermal muscle layer of the column, and, consequently, there 
is no infolding of the disc in contraction. 
The external tentacles are conical, numerous, and entacmez- 
ous. They are arranged in five cycles closely crowded together. 
The innermost cycle consists of 24 tentacles, as does also the 
next external, the third of 48, the fourth of 96, and the fifth of 
192; the third and fourth cycles being much crowded together, 
so as to look like one. Upon the inner faces of each of the 
tentacles are three or four transverse ridges which dilate into 
tubercles at either extremity, and are due, as sections show (PI. 
IV., Fig. 8) to an increased thickness of the mesogloea in these 
regions. Lesueur (17), in his brief description of this form, 
notes that “the tranverse tubercles are enlarged at their extrem- 
ities, sometimes bilobated”’; and I observed a tendency towards 
bilobation in some of my specimens. In Klunzinger’s specimen 
of P. loligo (77) the tentacles are “recht und links von der 
Mittellinie, mit kleinen rundlichen Warzen besetzt, die oft durch 
Querwiilste jederseits verbunden sind, wodurch sie wie gefie- 
dert sind. Andermal sind sie zu unregelmassigen Lappchen 
oder Gruppen verbunden wie Ehrenberg zeichnet.” The latter 
forms approach the Bahaman specimens more than those figured 
