'3+ 



trace of any marked grooves at either end (Fig. I.). Its 

 surface is owing to thickenings of its walls ridged over those 

 mesenteries, which are attached to it. If 24 septa fuse in the 

 axial fossa, there should be 48 mesenteries of a first order 

 reaching the stomodoeum and corresponding to ridges. If a 

 less number fuse, there should be a proportionately lesser 

 number of mesenteries with ridges on the stomodoeum, but 

 this is not so, three polyps with 18, 20 and 21 such septa 

 having 48 mesenteries with ridges and one with 24 septa 50 

 such mesenteries. In a case with 20 septa (Fig. I.) two of the 

 mesenteries out of pairs on each side of tertiary septa have 

 failed to reach the stomodoeum, but their places have been 

 taken by others bounding quaternary septa. 



The lower edge of the stomodoeum is ill-defined and often 

 in the contracted polyp somewhat turned outwards (Fig. II.). 

 Its thickenings pass directly into the filaments of the corre- 

 sponding mesenteries, which form a first order. 



Fig II. Diagrcjmmatical longitudinal section of a partially retracted specimen 

 of F. ruhrum, th? left half cutting a tentacle over a primary septum, expo.ing the 

 f dce of one of the bounding mesenteries, and the right half cutting a less retracted 

 tentacl>i over a quaternary septum and like wise exposing the face of one of the 

 bounding mesenteries. 



'I he longitn linal lines on thi faces of the mesenteries represent the distribution 

 and course (f the muscular fibres. Against the epith ca their attachment in 

 clusters is, to some degree, shown. 



e. tv. External body wall. t. Ten'acles. p. tc Wall of the peristome. »t. 

 Stomodoeum. m. /. Mesenterial filaments, ff. Generative o-gans (ovary oq the 

 1 ft and -estis on the right me.sentory). 7:'. Epitheea. 5 1 and S l septa of cycles 

 I. and IV., represented by incomjiletc lines. T. Trabeculae from the septal edge. 



Muscles. — The muscles are of the usual Actinian type, but 

 the circular sphincter is absent. The longitudinal muscular 



