Tlie Actiniae of tlie Plate Collectiou. 249 



Diesentery and paired representatives of tlie third, fourtli and fifth 

 rycles. In the latter it will lie seen tliat one individnal of eacli 

 pair is distinctly narrower tlian the otlier, tbe arrangemeut con- 

 forming to the rnle laid down by Carlgeen for the genus. 



All the mesenteries are very thin their at their Insertion into the 

 column wall, but increase rapidly in thickness as tliey are traced 

 inwards. The longitndinal mnscles are rather weak being borne 

 npon low and simple processes, vvhich, in the larger mesenteries are 

 set npon broad low elevations of the general snrface of the meso- 

 gloea, the result being that the mesenteries in section present an 

 nndnlating outline over the snrface occupied by the mnscles. The 

 parieto-basilar ninscle forms a slight fold, as shown in the third 

 cycle mesenteries represented in Fig. 33, and in some mesenteries 

 cavities occnrred along the line of fusion of the mnscle with the 

 surface of the general mesogloea. 



All the imperfect mesenteries. with the exception of the rudi- 

 mentar}' members of the sixth cycle, were fertile. The Single 

 speciüien in the collection was hermaphrodite ; the great majority 

 of the fertile mesenteries contained ova, but in a few cases spermatozoa 

 occurred in their stead. Thus in the larger member of the pair 

 belonging to the fifth cycle shown in Fig. 33 to the right, ova 

 occurred, while the smaller member of the same pair contained 

 spermatozoa, and in another pair, tliis time belonging to the third 

 cycle, the smaller member bore ova and the larger spermatozoa. 



I did not succeed in determining the occurrence of marginal 

 stomata, but oral ones were clearly present. 



I am inclined to snspect that this form will prove identical with 

 A. excelsa whicli I described (1893) from the "Albatross" collection. 

 The much greater thickness of the mesogloea and the remarkable 

 thinness of the sphincter, not to mention the hermaphroditism, seem, 

 however, to mark it as distinct. So long as the structure of only 

 one individual of a species is known, the amount of its variability 

 in any direction remains unknown and it is not impossible that the 

 diiferences between the present form and Ä. excelsa may be bridged 

 over by the study of additional individuals. It certainly seems 

 Strange that three diflferent species, A. excelsa, A. intermedia and 

 the present form, agreeing in many respects but differing principally 

 in the thickness of the column wall and in the sphincter, should 

 occur in nearly contiguous areas, when A. callosa has such a wide 

 distribution. 



17* 



