134 MR. W. L. SCLATER ON A NEW [Feb. 16, 
The ectoderm of the tentacle (Plate XIII. fig. 6) also contains a 
series of nematocyst batteries; the cells, however, differ from those 
of the knob in the following points: they are very much smaller, 
they are pigmented, from them are developed the longitudinal muscle- 
fibres ; in the endoderm of the main part of the tentacle the elements 
are not nearly so high as are those of the knob, and at their bases 
are found the circular muscle-fibres. 
The tentacle therefore differs little in structure from the actinian 
type as deseribed by Hertwig (7). 
The muscles are very weli developed on both sides of the mesen- 
teries ; the arrangement is shown in figures 8 and 9 of Plate XIV., 
where figure 8 represents the arrangement on the ectoccelic face, 
figure 9 the arrangement on the entoccelic face. The edge of the 
mesentery is occupied by a thick packed mass of mesenteric filaments 
above, and by the ova, also packed thick, below ; ova and mesenteric 
filaments seem to be well developed in all the mesenteries, except on 
the directives, where I have been unable to detect any sign of ova, 
but I have only been able to examine two directives, one of which 
was malformed, so that I am unable to make sure of this point. 
Plate XIII. fig. 7 represents a small portion of a section of a 
mesentery highly magnified, showing the folding of the surface on 
one side in order to increase the surface for the muscle-slips, but in 
no case have I detected the inclusion of masses of muscles in the 
mesoderm, as has been figured by Hertwig (7) m Aetinolobia and 
Tealia, and other Actiniz. 
The only example of this Coral I have been able to examine con- 
tained ova; no spermatozoa could be detected, so that the Coral may 
be considered dicecious. 
The development of the ova differs slightly from that described in 
the Actinians by Hertwig ; in Stephanotrochus the mesodermal lamella 
in which the ova lie is reduced to a thin string (Plate XIV. fig. 10), 
and the entodermal cells on either side have become very long and thin, 
resembling, perhaps, the ‘‘ Cambium Zellen” described by Weissman 
in certain Hydroids which nourish the ova at their own expense. In. 
the figure there will be seen several ovarian cells which have not yet 
entered the mesodermal lamella, but which are still lying in the 
endoderm ; and in one case there is an ovarian cell figured lying half 
in the endoderm and half in the mesodermal lamella; the ripe ovum 
is full of deutoplasm, and the germinal vesicle and germinal spot are 
very clearly seen. 
Besides the ovarian string, the mesenteric filaments can be seen in 
section ( Plate XIV. fig. 10), consisting of a mesodermal string and 
high endodermal cells, with many pigment-cells scattered among 
them ; they are cut in section in different planes. 
Beyond the ova the mesoderm again thickens slightly up to the 
end of the mesentery, where it splits to line the hard septal walls, 
since this section is from part of the mesentery low down where the 
mesentery is inserted between the columella and the two adjacent 
septa, all of which are lined by the mesodermal lamella with a layer 
of calycoblastic cells interposed. 
Calycoblastic cells were first detected by Heider (8), who showed 
