476 G. HERBERT FOWLER. 



functions. This second alternative has evidently affected me- 

 senteries 3 (fig. 12), but no others. 



It is possible that the exaggerated development of retractors 

 has occurred in mesenteries 1, 2, 4, 6, in consequence of the 

 larva of Octineon being of the type figured as A (p. 470) . Very 

 interesting are the special muscles of mesenteries 3^ in which 

 the direction of the fibres is approximately at right angles to 

 those of the retractors; as stated above, they are probably to 

 be ranked as depressors, — muscles which, if present in other 

 Actiniaria, have not yet been distinguished, and therefore are 

 only slightly developed : their occurrence here, like the shifting 

 of the retractors, indicates the very great specialisation which 

 Octineon has undergone. 



To the Zoanthid habit of incrustation of the external surface 

 of the mesoglosa we can hardly attribute systematic import- 

 ance, although it has not yet been described as occurring out- 

 side the group. 



The evidence seems, therefore, in favour of the view that 

 Octineon is the type of a new and highly specialised family, 

 descended from true Hexactinian ancestors. 



