No. 1.] ACTINIARIA OF THE BAHAMAS. 45 
rounded elevations. The arrangement of the mesenteries I 
was not able to make out satisfactorily. The majority of them 
are perfect, the imperfect ones being usually quite small and 
appearing to have no regular arrangement. Thus there would 
be several perfect pairs in succession, followed by one or two 
imperfect pairs, alternating with perfect ones, and then several 
more perfect pairs, and so on. It would seem that normally all 
the mesenteries are perfect, but that a few, for some cause or 
other, remain undeveloped. All the mesenteries are situated at 
equal distances, so that the intra- and inter-mesenterial spaces 
are about equal in width. It is difficult, owing to this and to 
the very slight development of the longitudinal muscles, to orient 
the pairs properly, but there are probably two pairs of directives, 
as in other forms, although I was able to make out with cer- 
tainty only one of them. R. Hertwig (82) has described a 
species in which this is the normal relation, and has founded 
upon it the tribe Monauleze. In its general character, however, 
Rhodactis differs greatly from Scytophorus, the only genus at 
present known to belong to the tribe, and on the other hand 
resembles forms which possess the two pairs of directives, so 
that I believe that it possesses the second pair, and that its 
apparent absence in the specimens examined was due to the 
unsatisfactory nature of the preparations which I studied. The 
number of the mesenteries is comparatively large ; in a small 
specimen I counted 48 pairs, and in another 52; but in a larger 
one, judging from the number of the series of ectodermal ele- 
vations, there must be in the neighborhood of 150. 
The endoderm of the mesenteries is of the same nature as 
that of the disc, and requires no further description. Imbedded 
in it were found in the specimens examined numerous cysts, 
measuring about 68 w in length by 27 w in breadth, which looked 
almost like encysted nematode parasites, the comparative rarity 
of their occurrence lending somewhat to the illusion. Careful 
study, with high magnification, showed them to be large nema- 
tocysts. The thread contained in the interior is not very long, 
and is finely and obliquely striated. Occasionally considerable 
numbers of these bodies occur together, apparently more espe- 
cially in the mesenterial filaments, but their number taken alto- 
gether is comparatively small. They were present in the endo- 
derm of the disc (Pl. IV., Fig. 2, ze) as well as in that of the 
