ZOANTHARIA g^ 



S. gracilis, I have often obtained both in Isozoanthus and Parazoanthus species. It is difficult especially 

 to obtain good figures of the entodermal sphincter in those polyps where the mesenteries lie very 

 close together, for in such cases the section cuts not only the body-wall but also at the same time a 

 mesentery. As E. gracilis is a form with small polyps and with numerous mesenteries, the section lias 

 certainly at one and the same time cut through the body-wall and mesenteries. I tluis believe, that 

 S. gracilis is a Parazoanthus species (a fact that lywowsky in a letter to me seems willing to accept). 

 Under such circumstances the additions in the diagnosis wliich Lwowsky makes witii regard to the 

 sphincter and encircling sinus must be dropped, for tlic indication of an encircling sinu.s, which the 

 ectodermal canals are said to form in .S'. balanorum, has little resemblance to a true encircling sinus 

 especially in the upper part of the polyp. 



Thus the assumption, that an encircling sinus occurs in Epizoanthus, must also be rejected, 

 though it is not inconceivable theoretically, that such may occur there. Wlien we see, namely, that 

 the macrocneinic Zoanthidae with entodermal spliinctcr may have (Parazoanthus) or lack (Isozoanthus) 

 an encircling sinus, it is quite possible, that the same condition may be present in the macrocnemic 

 Zoanthidae with mesogloeal sphincter. In this case it might be advisable to set up a new genus for 

 forms with encircling sinus, distinct from Epizoanthus. Nevertheless S. gracilis cannot be taken as a 

 type for this conceivable genus and just as little, it .seems to me, S.balanoruvi. 



Lwowsky states, that a specimen of Fipiaoaiitliiis norvcgiciis examined by him had a l)rachyc- 

 nemic arrangement of the mesenteries (I.e. p. 6o8j and thinks it probable, that Haddon and Shack- 

 leton (1891), just on account of the external habitus and the appearance of the sphincter, had concluded 

 that this species was an Epizoanthus. Since Haddon and Shackleton in their .short notice on this 

 species remark upon the appearance of the incomplete mesenteries, they have certainly also examined 

 the arrangement of the mesenteries. The specimens I have examined here above show a macrocnemic 

 arrangement; 2 other specimens, of which I made sections, had the same arrangement. Lwowsky's 

 specimen has thus — unless some mistake of locality has taken place — been a malformation, which 

 sometimes occurs both in brachycnemic and macrocnemic Zoanthidae, the brachycnemic showing a 

 macrocnemic type and the macrocnemic a brachycnemic, but only exceptionally, so far as I know 

 {Polythoa cariba-a), on more than on side of the body (Carlgren: Beobachtungen iiber die Mesen- 

 terienstellung der Zoantharien etc. Festskrift for Lilljeborg 1896, fig. 6a PI. 8; Dnerden: Jamaican 

 Actiniaria PI. i, Zoantheae Sc. Tran.s. R. Dublin Soc. 6 (2) 1898 p. 331; this work p. 34). Further, dis- 

 arrangement of the mesenteries sometimes occurs (Carlgren 1896 1. c. PI. 8, fig. 5 a, 7). That a 

 brachycnemic species should occur in Trondhjem Fjord is indeed little conceivable, since we know of 

 no brachycnemic forms from European seas; these belong to tropical and subtropical seas. In any case 

 Lwowsky's colony of E. norvcgiciis certainly merits closer examination. 



Finally, I wish to point out an oversight of Lwowsky, which may possibly be mi.sleading for 

 his readers. On p. 568 he identifies "the reflected entoderm" with the cnido-glandular region instead 

 of with the ciHated tract of the filaments (cf. Haddon & Shackle ton's figs, i, 6, PI. 60. 1891). 



I cannot conclude this appendix without emphasizing, that our investigations on the various 

 Zoanthidae species require to be extended, if we are to reach more accurate knowledge as to whether 



