252 G. HERBERT FOWLER. 



They are covered by small prominences, each of which is a "battery" 

 of nematocysts. I have not been able to determine whether they 

 possess an opening at the tip or not. They vary in size and position 

 according to the order to which they belong, the primary tentacles 

 being the largest and nearest to the mouth. (Vide Moseley (II), pi. 

 xvi, fig. 12.) 



The mouth is oval in outline, and at each end of its long axis there 

 is in most cases a well-marked gonidial groove. 



Through the periphery of the mouth-disc protrude the acontia. I 

 have by a fortunate section been able to satisfy myself that they are 

 ejected through definite openings, not by rupture of the disc ; these 

 are therefore directly comparable to the cinclides of Actiniae. 



A mesentery of the first order is drawn in fig. 5 to show the general 

 trend of the muscles, though they are much more numerous than 

 there represented. They are best seen by mounting the mesentery 

 whole in glycerine. 



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 (exocoelic) faces are 

 ranged the protractors, oblique in direction ; these differ slightly in 

 the species, being confined in Fl. alahastrum 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 

 approximately 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 entocoelic) 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 communication. 



Both the primary and secondary orders of mesenteries are attached 

 to the stomatodseum for its whole length ; the tertiaries are attached to 

 the mouth-disc, but, as the latter passes imperceptibly into the stoma- 

 todeeum, no importance is to be attached to this. 



