ZOANTHARIA 



characteristics, which liowever are often so little distinct, that an identification is only possible in 

 exceptional cases. This is all the more difficult as tlie group of Zoantharia evidenth' comprises many 

 species that are probably in process of differentiation. An attempt to bring some order into the 

 classification was tried in 1891 by Haddon and Shackleton, who quite reasonably founded their 

 classification on anatomical characters. Other scientists, as Duer den and several others, have followed 

 in their footsteps but we are still without sufficiently good characteristics for the separation of quite 

 a number of species. 



Thus, many of the characteristics on which the classification of the species has been founded 

 are found to be of small importance. Regarding the appearance of the coenenchyme, firstly, it may 

 sometimes give ns good hints but we still know too little of its variations, which are caused by the 

 object on which the ccenenchyme is fixed. That a variation takes place is almost certain, but its 

 limits cannot l)e determined as yet. That the cojnenchyme may have a different appearance in the 

 same species is seen in Ei^izoanthus incrustatus, which ma}- have both a carcincecium-forming ccenen- 

 chyme and a slightly tube-shaped coenenchyme, on the supposition that the free variety barlesi of 

 E. incrustatus belongs to this species. Pax' investigations of West Indian species of Palythoa seem 

 to indicate, that a variation occurs, even though it seems possible here that separate species have 

 been dealt with. The canal-system in the coenenchyme might also be of use for the separation of 

 the species, though but very little information thereon has been published as yet. 



The outer appearance of the polyp may sometimes show very good characteristics for identi- 

 fication, but tlie .species are often so little distinguished from each other that two polyjjs alike in 

 outer appearance may nevertheless belong to 2 different genera (cf. e. g. figs. 13, 19, PI. i). The relation 

 between height and breadth has been used for differentiation of species, but is such a weak character 

 that the different degrees of contraction in different polyps may change the proportion between height 

 and breadth. Even the capitular region and the distal contours of the polyji are always somewhat 

 different in appearance according to the amount of contraction. Thus, the greatly distended polyps 

 of one species cannot be summarily compared with the greatly contracted ones of another. The 

 furrows on the capitulum, which generally correspond to half the number of mesenteries, are also a 

 much used, .specific character, but this method has the fault, that the character is variable, as furrows 

 are not always found corresponding to the joungest mesenteries and the number of mesenteries and 

 thus also the number of capitular furrows change according to the age of the polyps, the older ones 

 having more mesenteries and consequently more capitular furrows than the younger, and even in the 

 former a variation also occurs though within certain limits. In characterising the species according 

 to the capitular furrows, it is thus necessary to pay attention to well-developed polyps, which often 

 necessitates having large material. 



Most of the Zoanthidae are, as already known, incrusted with foreign bodies, foraminifera, 

 sand-grains and sponge needles. Regarding the incrustation generally, it seems in each separate 

 species to consist of the same material, as shown by Haddon and Shackleton, though small 

 variations naturally always occur; but I know more than one case, especially in I. bulbosus, where 

 two different specimens of the same .species have had quite different incrustations, for which reason I 

 think it possible that similar conditions may be observed among other species. Though, in my 



