24 G. HERBERT FOWLER. 



except occasionally the remains of the mesogloea lamina of a mesen- 

 tery. Into this the living tissues pass gradually. 



The tentacles, which are both ectoccelic and entocoelic, i.e., one 

 over every septum, are knobbed, each knob being such a battery of 

 nematocysts as has been described in Flabellum (2), Stephanotrochus 

 (11), &c. 



The mesenteries, which, like the septa, vary in number in different 

 polyps, all bear retractor muscles on their entocoelic faces, i.e., there 

 are no pairs of " directive " mesenteries at the opposite ends of the long 

 axis of the oval stomatodgeum, thus differing from those of all other 

 Hexactinise or Madreporaria yet described. The significance of this 

 fact cannot, of course, yet be understood, as nothing correspondingly 

 abnormal occurs in any other part of the polyp with which it might 

 be correlated. As, however, the mechanical or other function of 

 the directive mesenteries is itself not yet explained, the meaning of 

 the variation from the common type is naturally not appreciable. 

 The number of the pairs of mesenteries, like that of the septa, is not 

 necessarily a multiple of six. 



The only point in the histology that appears worthy of note is 

 the great length of the calycoblasts, as compared with that of the 

 other cell-elements. A group of them from the edge of a growing 

 septum is represented in Fig. 7. Still more marked is the great 

 length of these cells in Fig. 8, which represents a transverse section 

 through the tissues at that point where the upward growth of the 

 theca divides the mesenteries into a central portion within the calyx, 

 and a peripheral portion outside of it. Here they measure as much 

 as '054: mm. The large plate of mesogloea in the centre of the figure 

 is merely that which immediately overlies the lip of the calyx, and is 

 cut in a direction parallel to its flattened surfaces, while the section 

 passes nearly at a right angle to the other tissues. The point 'here 

 figured is such a " centre of calcification " in the theca as has been 

 already referred to (vide p. 22). 



hi. Summary. — The most important facts thus obtained are : — 



1. The polyps agree with the normal Actinian type, exoept/or the 

 absence of " directive mesenteries." They possess a well developed 

 " Eand-platte."* 



* It is, perhaps, unnecessary to coin an equivalent for this till its morphological 

 value is better understood. 



