Stkphenson — Certain Actiniaria collected off Ireland. 1 la 



North Sea, described by G. L. Walton (56), there were also 77 pairs of mesen- 

 teries, and about 127 tentacles, some having been thrown off. ft is curious 

 that three specimens of this species should all have 77 pairs of mesenteries 

 only, and suggests that possibly that is about the maximum to be attained in 

 this case. 



(iv) Through the kindness of Dr. E. J. Allen I have been able to examine 

 externally another North Sea specimen identified as B. tuediae, as regards 

 external characters. This agreed exactly in all essentials with the specimen 

 I have described as (i) above, but had even smaller (proportionately) and 

 blunter tentacles; they were in four cycles only — 12, 12, 24, 48; but the 

 whole specimen was smaller than (i). 



Musculature. —For convenience of reference I will number the three speci- 

 mens with which I have to deal according to the order in which they are 

 above mentioned, (i) is the specimen in PI. XIV, fig. 2. (ii) is the other Irish 

 specimen, without tentacles, (iv) is the North Sea specimen borrowed from 

 Plymouth. 



A. Sphincter. — I have figured four sphincters in PI. XX. Figs. 1, 5, and G 

 are from different specimens of B. tuediae (on slightly different scales) ; fig. 7 

 is from an Irish B. longicomis. Fig. 1 is from specimen (i), fig. 5 is from 

 specimen (ii), and fig. 6 is from (iv). The sphincter is, of course, endodermal, 

 fairly strong, diffuse, with high, fine, much-branched processes, even tending 

 sometimes to anastomosis. It is difficult to be definite in speaking of the 

 differences between tuediae and longicomis, and of course the sphincters of 

 the different specimens of B. tuediae vary considerably among themselves, but 

 one may say that (a) all the tuediac-s^hmcteis are of one type ; (b) the tuediae 

 sphincter has a tendency to be shorter and proportionately broader and rather 

 more definite than in B. longicomis (cf. fig. 7), even though this difference is 

 less marked in the "Terra Nova" longicomis than in our northern form. 



The tuediae sphincter has a tendency to produce "humps" of mesogloea at 

 different points in its course, but these may be present or absent, ami may 

 vary in position from the top end of the sphincter (see fig. 5) to the bottom 

 end (fig. 6), even in the same specimen at different parts of the margin. And 

 the presence of these " humps " does not seem directly dependent on the inser- 

 tions of outer tentacles. The type of sphincter, therefore, seems distinct from 

 the type figured by Kwietniewski for B. Icerguelensis, and by McMurrich for 

 B. pannosa (see 28 and 30), for instance. In these latter the mesogloea at the 

 upper end of the sphincter sends out a kind of twig of mesogloea, which is 

 larger and more branched than the others. In L'.tiiediac, the " humps " al 

 various levels are hardly of this nature, and may perhaps be due to mere 

 contraction of the wall. 



[Q2 



