ZOANTHARIA 



of which the basal part of the spiral thread is fairly distinct; more seldom and more scattered we 

 also find some nematocysts of the same kind as in the body-wall. In the filaments we find the same 

 sort of capsules as in the body-wall, sometimes in two different sizes, and also some thick-walled 

 capsules through which the basal part of the spiral thread can be seen and often, further, typical, 

 transparent thick-walled capsules. 



Though I hope that the nematocysts of the Zoantharia species may be of use in the identifi- 

 cation of these species and make this to some extent easy, I am however fully aware that we are 

 still far from having discovered the special characters of many species. The large number of 

 Zoanthidae described in this paper may appear surprisingly great to many Actiniae specialists. But 

 I would remark, that the material investigated from northern and arctic seas is undoubtedly the 

 largest that any scientist has had for examination. It is of course quite possible, that later investiga- 

 tions may show, that some of the species described here are varieties of other species or that what 

 is considered a variety here may come to be regarded as a separate species. Taken on the whole, I 

 feel convinced, however, that the number of species will not be much reduced, as most of the species, 

 of which I have had a rich material, are certainly good species. 



As already pointed out in 1900, the distribution, size and structure of the nematocysts are in 

 the Actiniae of no small importance for the identification of the species, a theory that has been con- 

 firmed by my later investigations on the Actiniae. Pax doubts their importance, but so far as I can 

 find, he has not made any extensive investigations on a large number of species to clear up the 

 question. He admits, however, that in a few cases the capsules may serve as good characters. As 

 evidence for his view he refers to some measurements made by me on 3 species belonging to the 

 genus Actinioides and finds them to be almost the same, from which he draws the conclusion that 

 the nematocysts are of no great importance for the classification. I do not agree with him here, for 

 the same might be said about any organs of the species, if we agreed with Pax's standpoint. How 

 often do we not find, that the sphincters, the arrangement of the mesenteries and a great many other 

 organs show agreement in many species of a genus of Actinaria, yet nobody would deny their great 

 importance for the classification of this group. The occurrence of certain kinds of nematocysts, their 

 size and arrangement, is a character as good as any, even if it is not always of importance for the 

 separation of closely-related species. For the separation of many genera of Actinaria they may also 

 be used with advantage, for, so far as I have found in the abundant material investigated, many 

 genera have nematocysts of a certain nature and arranged in a certain manner. It is at any rate a 

 fact, that the nematocysts are found to be indispensable for the separation of the species, as soon as 

 the expert has recognized their utility. In some cases, I may say, it is only a closer study of the 

 nematocysts, which has given a starting point for the separation of the species belonging to two 

 nearly allied genera species which showed so great a resemblance that it would hardly have been 

 possible to separate them, had not the different size of the nematocysts in certain parts of the body 

 opened up the possibility for a grouping of the species. In another paper I shall deal further with 

 these features. I would therefore recommend those who write on the Actiniaria, to pay particular 

 attention to the arrangement and structure of the nematocysts, being convinced that many systematic 

 errors would be avoided if the capsules were only subjected to a proper examination. 



