Part II.—Stichodactyline and Zoanthee. 153 
wall within the mesenterial spaces 1s sometimes much elevated. The number of 
mesenteries is considerable, one small specimen possessed fourteen complete pairs, 
and another eighteen. The mesoglea is very thin, and the vertical retractor muscles 
are extremely weak, so as to render it almost impossible to determine the directives. 
I have been able to definitely ascertain the presence of the latter in only one 
instance, but others may occur. The parieto-basilar muscle, though weak, is 
clearly distinguishable on each side. ‘The endoderm is a thick, highly glandular 
layer, and medium-sized stinging cysts are abundant in places. In some instances 
the ccelenteron appears filled with the mucus extended from the endoderm cells. 
The mesenterial filaments consist only of the middle glandular streak or Nes- 
seldriisenstreif, the lateral ciliated streaks or Flimmerstreifen being absent (PI. xt., 
fig. 4). They are seen to originate in direct continuity with the ectoderm of the 
stomodeum. At first, owing to the strongly folded condition of the stomodeeal ecto- 
derm the mesenterial filament is irregular, or rather the appearance is presented as if 
a portion of the terminal region of the stomodeeum were still connected with the free 
edge of each mesentery. It is only a little below the stomodeeum that the ordinary 
rounded appearance is assumed, but the Nesseldriisenstreif is never clearly marked 
off from the mesenterial epithelium (PI. x1., fig. 4). The nematocysts in the upper 
region are elongated and narrow, but below they are much larger, oval, and 
strongly spinous. Different stages in the growth of the large tuberculated 
nematocysts can be distinguished, the contents of the younger staining deeply 
with carmine. The mature individuals present a peculiar appearance when a group 
is cut through transversely. Irregular spine-like projections extend all the way 
round the thick horn-coloured wall, the interior appears filled with some coagu- 
lated substance, and here and there a cut end of the thread is indicated. The 
spiral threads themselves are finely and regularly spirally marked. ‘Towards the 
free end of the mesenteries in the lower regions the endoderm is often loaded 
with zooxanthelle. 
Of several specimens sectionized, only one contained reproductive organs, sper- 
maria apparently in a dehiscing condition (Pl. xm, fig. 8). The reproductive cells 
are found in the interior of the mesoglea, and in escaping break through the endo- 
dermal tissue. They occur in only a few of the mesenteries. 
In three polyps dissected in the living condition, a few embryos were found. 
They are large, dark-green, ovoid bodies, slightly narrower at one end, and 
about 1 mm. in length. On cutting open the animal, they escaped freely into the 
water. 
Prof. M*Murrich (1891, p. 803) found that the polyps retain the embryos in 
the interior of the body until they are furnished with two or four perfect mesen- 
teries. During the month of September I observed examples in process of partu- 
rition, ‘The disc and upper part of the column were almost entirely infolded, 
