Part I1.—Stichodactyline and Zoanthee. 201 
out of numerous examples sectionized, I have been able to definitely ascertain 
the macrocnemic arrangement in several. 
The mesenteries below the stomodzeum are very short in transverse sections, 
and extend but a little distance vertically ; two or three are continued for some 
way below the others, but which are in relation to the directives could not 
be determined. As the free edge of the mesentery leaves the stomodeum 
it becomes deeply concave. Owing to this, and the shortness of the stomodzum, 
the perfect mesenteries in transverse sections of some retracted polyps appear 
free even before the stomodzum is reached, one half being still connected 
with the concave disc, and the other with the column-wall, each with the fila- 
mental tissue at its free termination. 
The endodermal epithelium of the mesenteries resembles that of the body- 
wall, and contains many zooxanthelle. 
In the upper region of the polyps, the mesenterial mesogloea as it leaves the 
column-wall is much and irregularly thickened, and contains cell-islets, but 
beyond this the layer is extremely thin. ‘There is a distinct indication of a 
parieto-basilar muscle on each side, but the longitudinal musculature is not 
sufficiently developed to allow of a study of the paired arrangement of the 
mesenteries being made. 
No reflected ectoderm occurs on any of the mesenteries. In transverse 
sections around the termination of the stomodeum an appearance of such is 
presented, but it is merely the Drtisenstreif which here runs horizontally. The 
tissue is never folded, as is usually the case, with the reflected ectoderm, while 
granular cells and nematocysts are present im addition to the supporting cells. 
Vertical sections also reveal a similar absence. 
For some little distance from their origin at the stomodeum, the filaments in 
section have an irregular outline. They are simple throughout their length, 
consisting only of the middle lobe or Driisenstreif. In the lowermost region 
the mesenteries may divide at their free edge into three branches, each capped 
by a filament which is cordate in transverse section. The latter is sharply 
cut off from the rest of the mesentery, and stains much more deeply. The 
mesenterial endoderm is usually thickened immediately behind the filament, 
in some cases partly surrounding the filament; otherwise it differs in no important 
respect from the remaining mesenterial epithelium. 
No gonads were present in any of the numerous examples sectionized. 
The form described above was trawled on several occasions from a depth of 
10—14 fathoms on the Pedro Banks, Caribbean Sea, embedded in the superficial 
tissues of some massive, dark-coloured sponges. From the number of sponges 
trawled, each bearing the commensal Zoanthid, the species must be very abundant 
