338 J. E. Dueeden — Jamaican Actiniaria : Part I. — Zoanthex. 



(Esophagus. — The nematocyst and nuclear zone in the ectoderm is very- 

 regular, and situated close to the outer surface, while a non-staining 

 nervous tissue intervenes between it and the mesogloea. The latter is very- 

 thin, and the endoderm resembles that of the mesenteries. In transverse sections, 

 the oesophagus is oval. In the upper region, the ectoderm is not thrown into 

 folds, and the oesophageal groove is barely apj^arent. Lower, as many as twelve 

 longitudinal folds may be present on each side, and a slight indication of a 

 groove. The mesenteries are attached to the oesophagus at about equal dis- 

 tances all the way round. The ectoderm is reflected on the mesenteries, and 

 continued downwards as the mesenterial filaments. 



Mesenteries. — The mesenteries are of the brachycnemic type ; generally about 

 thirty pairs are present ; one specimen had fifteen perfect mesenteries on one 

 side, and only thirteen on the other. 



The endoderm contains abundant zooxanthellse, and medium-sized oval nemato- 

 cysts. The digestive endoderm (1889, p. 116; 1891, p. 622) is not very thick. 



The basal canal is large in both the perfect and imperfect mesenteries. It 

 is elongated in the former, and full of deeply-staining cells. 



The parieto-basilar muscles are clearly distinguishable, as also the retractor 

 muscle of the mesenteries. The mesogloea is folded to support the muscle. 



Gonads. — No reproductive elements were present in any of the examples studied. 



The following may be regarded as distinguishing anatomical characters: 



(a). Pigment limited to the inner portion of ectoderm ; 



(b). Mesoglceal lacunas ; 



(e). Form of sphincter muscle. 



The Jamaican form above described appears to unite the two species Z. 

 Bolandri and Z. dubia, as originally described by Lesueur, and as known to 

 Duchassaing and Michelotti from the same localities. Considering the variation 

 in colour noted, it is evident that little importance can be attached to it. 

 Referring to the first species, Duchassaing and Michelotti state : "Le couleur de 

 cette espece est sujet a varier, mais nous n'y avons jamais reruarque" a l'dtat 

 vivant la teinte qui lui donne M. Milne-Edwards dans l'atlas qui accompagne son 

 ouvrage sur les coralliaires, la teinte verte se montre toujours dans une parti 

 ou sur la totality du corps de ces animaux." Some account must be taken of 

 the character given by Lesueur that, when the animal is contracted, the summit 

 is marked with deep blue angular spots and white lines, a feature agreeing with 

 the present specimens. The polyps are usually non-pedunculate, resembling the 

 figure of Z. dubius given by Duchassaing and Michelotti ; but pedunculate forms, 

 agreeing with Lesueur's original figure, also occur. 



