590 
a. HERBERT FOWLER. 
continuous with the transverse fibres of the mesentery ; on the 
central face oblique fibres. 
The stomodseal ectoderm is not essentially different from 
that of the mouth-disc ; and, though there are well-marked 
gonidial grooves (food grooves, Mundwinkelfurchen), they 
show no differentiation of ectoderm comparable to that of 
Alcyonarians (the “ siphonoglyphe ” of Hickson). 
The whole of the coelenteron is lined by endoderm of 
cubical or columnar cells ; generally it is only one cell deep, 
and in the living animal presumably ciliated throughout. At 
the point where it passes into the thickening known as the 
mesenterial filament (if that be indeed endodermal in 
origin) its characters change, and the number of nuclei 
increases enormously, together with the length of the cells. 
Its histological appearance entirely bears out what physio- 
logical investigation has also shown for the similar filament in 
Actiniae, that it is secretory in character, producing a prote- 
olytic fluid (fig. 10). 
Nematocysts do not occur apparently in the true mesen- 
terial filament, but oulv on that portion of it which is con- 
tinued on to the contorted lamellae, which I regard, in part at 
least, as equivalent to the acontia of Actiniae. Those occurring 
on the tentacles are of a different size and shape from those 
which characterise the acontial filament, though in the latter 
both forms are found. The smaller, occurring on the tentacles, 
is '06 mm. x '01 mm. ; the larger, which is only to be found 
on the acontial filament, is - 1 mm. x '025 mm. The thread 
of the latter form is covered with minute barbs, which give it, 
when coiled up in the capsule, a granular appearance. 
Rhodopsammia Parallela (Semper.) 
This form, belonging to the family Eupsammidae, affords a 
very good example of a perforate Madreporarian. Budding 
sparsely, it forms no coenenchyme, so that the polyp can be 
studied easily and without the complications incident to coenen- 
chymatous species. 
i. Of the Corallum the systematic characters have been 
