ON ELOACTIS MAZELI. 79 



the 11th family of the Heteractinae with several other anemones whose 

 internal structure is unknown. 



The elongated form of the body, the absence of a definite sphincter 

 muscle, and the presence of a small number of mesenteries, are characters 

 of Eloactis which show that it is related to the primitive, rather than to 

 the more advanced anemones : the latter do not possess an elongated 

 body, but are characterized by the presence of a definite sphincter muscle 

 and a large number of mesenteries. The Edwardsidse and the Hal- 

 campidae are two of the most primitive families whose members have an 

 elongated body form, no definite sphincter muscle, and a small number 

 of mesenteries. The Edwardsidse have eight mesenteries, whereas in 

 E. nuizeli there are twenty ; therefore Eloactis cannot be placed with 

 Edwardsia, the sole genus of that family. 



The family Halcampidse has been defined by McMurrich in the pape^ 

 already referred to (2), as "Actiniae with a small number of mesenteries, 

 six, ten, or twelve pairs being all present ; longitudinal muscle pennons 

 narrow, but strong ; no special sphincter muscle ; conchula present or 

 absent ; base usually rounded and vesicular." In this family, therefore, 

 McMurrich places Halcurias and Peachia as well as the genus Halcampa. 

 Eloactis, with a small number of mesenteries and no sphincter, may 

 be placed in the Halcampida^. It may be closely compared with Hal- 

 curias pilatus, as described by McMurrich, and both are found to possess 

 the following characters : — 



Column cylindrical ; ten pairs of mesenteries, all of which are perfect. 

 There is no special sphincter muscle, and the tentacles are not covered 

 after contraction. 



There is one siphonoglyphe, and on the surface of the stoma- 

 todaeum are numerous ridges. 



All the mesenteries bear reproductive organs. 

 The mesogloea is fibrillar, especially towards the inner surface. 

 Halcurias has an adherent base, whereas the members of the Hal- 

 campidae have a rounded and vesicular base. Eloactis mazeli and 

 Eloactis producta have indications of a slightly adherent base ; but in 

 these three forms this character is outweighed by the small number of 

 the mesenteries and the structure of their muscles. 



The structure of E. mazeli shows that this form is slightly more highly 

 specialized than Halcurias pilatus. In the latter, the four pairs of mesen- 

 teries situated in the sulco-lateral and lateral intermesenterial spaces 

 are less extensively developed than the other six, and the siphonoglyphe 

 is neither deep nor well defined. On the other hand, E. mazeli has 



