588 
G. HERBERT FOWLER. 
In the arrangement of the longitudinal muscles on the 
inner (entocoelic) faces of the mesentery Flabellum agrees with 
Actinia; these are the retractors of the polyp. On the outer 
(exoccelic) faces are ranged the protractors, oblique in direc- 
tion ; these differ slightly in the species, being confined in FI. 
alabastrum to the upper third of the mesentery, while the 
longitudinal fibres extend for its whole length. Both sets of 
fibres are continued into the tentacles ; the oblique muscles of 
the mesentery becoming their external longitudinal coat, the 
longitudinal muscles of the mesentery passing into the internal 
and approximating circular fibres of the tentacle. This 
apparent change of direction will be understood by fig. 5. 
The two pairs of “ directive mesenteries ” at the ends of the 
longer axis of the mouth appear to possess the same general 
direction of the muscle-fibres, though bearing them on reverse 
faces; but the oblique protractor muscles (in this case ento- 
coelic) are, proportionately to the retractors, somewhat more 
strongly developed, implying perhaps that the expansion of the 
polyp is their especial function. 
There are no perforations through the mesenteries, such as 
are described in Actiniae, putting the chambers in communi- 
cation. 
Both the primary and secondary orders of mesenteries are 
attached to the stomodaeum for its whole length ; the tertiaries 
are attached to the mouth-disc, but, as the latter passes imper- 
ceptibly into the stomodaeum, no importance is to be attached 
to this. 
What Moseley ( 11 ) has termed “the contorted mesenterial 
filaments,” a mass of coils lying on the side of the mesenteries, 
appear to me after careful investigation to be, in part at least, 
organs corresponding to the acontia of Actiniae, namely, long 
lamellar offsets of the free edge of the mesentery, with one 
edge thickened to correspond to the mesenterial filament, and 
charged with very large nematocysts. They protrude in some 
instances, as above stated, through definite openings in the 
mouth-disc. Their exact origin from, and relation to, the 
mesenteries I have not been able to detect owing to the brittle 
