648 ME. J. E. DUEEDF.lSr ON THE EELATIOKS OF 



similar to that in Splienotroclnis, in two or three West-Indian 

 corals. 



McMurrich draws particular attention to the weakness of the 

 musculature in botli BTiodactis and Bicordea, regarding it, and 

 the absence of a sphincter muscle, as of family importance. 

 With respect to that of the mesenteries in B. Sancti-Thomcey 

 he writes : " The mesenteries, like the other regions of the body, 

 have the muscular layers very weakly developed, the longitudinal 

 foldings of the mesogloea, so characteristic in other species,- 

 being almost undeveloped and represented only by very slight 

 rounded elevations." The same remark may be applied to the 

 two species of Corijnactis that I have examined ; the mesogloea 

 of the mesenteries never discloses more than slight foldings for 

 the support of the musculature (1896, pi. vii. fig. 9). 



Studying together sections of the mesenteries of Corynaciis 

 and Cladocora, there is the closest similarity in their appearance, 

 both in the homogeneity of the mesogloea and in the weakly 

 developed retractor muscles. The dilfuse endodermal sphincter 

 of C. australis and G. viridis (1896, pi. viii. figs. 10 & 11) should 

 also be compared with that given by Fowler of SpTienotrochus. 



With the exception of its well-known presence in Cerianthus,- 

 a columnar ectodermal musculature was until lately regarded 

 as a rare feature in Actiniae, but now many genera and species are 

 known to exhibit such. Hertwig (1888, p. 12) first recorded 

 an ectodermal muscle in Gorynactis (?) sp. and a very weak layer 

 in Gorallimorplius ohtectus, comparing its presence with that in 

 Hydroid polyps and Scyphostomse, where the ectodermal system 

 is well developed. McMurrich (1893, p. 143) has since met with 

 it in Salcurias pilattcs belonging to the primitive Halcampids ;; 

 Carlgren (1893, p. 23) adopts it as a character for the whole of the 

 Tribe Protanthese ; Appellof (1893, p. 8) found it in Ptychodactis 

 patula ; while I have ascertained it to be well developed in two 

 species of JBmiodeopsis (1897), and in Gorynactis myrcia and 

 G. australis, and to be very weak in Phymanthits crucifer. 



In all these cases the muscle-layer is associated with an ecto- 

 dermal nervous system on the column, and with a like muscular 

 and nervous development in the ectoderm of the stomodseum, 

 while the sphincter muscle is absent or but feebly represented; 

 Chalmers Mitchell (1890, p. 555) made out the presence of a 

 thick longitudinal ectodermal muscular layer in the stomodseum 

 of Phymanthus (Tkelaceros) rhizophorce. 



