ACTINIARIA 



of the forms without acontia. Are the Edwardsids to be placed together with the Halcampids, as proposed 

 by Me. Murrich; are the Siphonactinids = Peachiidae to form a particular family; are the Halcampids 

 (s.lat.) with mesogloeal sphincter, and those lacking one, to be united in a single family; and finally, is a par- 

 ticular family to be established for the genus Ilyanthus ? Concerning the first question, which is closely con- 

 nected with the third, I must at any rate positively refuse the attempt to place the Edwardsids together 

 with forms provided with a mesogloeal sphincter, viz. the Halcampids (s. str.). The only principal point of 

 view for the arrangement of the other Athenaria is namely, in my opinion, the structure of the sphincter and 

 its occurrence. Most of these forms are devoid of sphincter, some have a mesogloeal and a few a rather well- 

 developed, endodermal one. Why should we not apply this feature as a basis of classification in this case, 

 when in the more differentiated Actiniaria with basilar muscles we lay so much stress, and with full right, 

 on the appearance of the sphincter as a basis for the arrangement of the families ? We distinguish the family 

 Actiniidae from the Paractiidae mainly by the structure of the sphincter, in as much as the sphincter is lacking 

 or endodermal in the first family, but mesogloeal in the second. If for instance the genus Paractis should 

 turn out to be provided with an endodermal sphincter instead of a mesogloeal one, it would no doubt by all 

 authors be referred to the family Actiniidae. As we cannot suppose that the mesogloeal sphincter is developed 

 in another way in the Athenaria than in the more differentiated Actiniaria I at least cannot find anything 

 tending to prove that the mesogloeal sphincter of the Halcampids variates, so as to make it now endodermal, 

 now mesogloeal, with transitory stages between 1 ; in the genera Hakampa, Parahalcampa and Cactosoma the 

 sphincter is mesogloeal and conspicuous, in Halianthella strong and even double it seems most consistent 

 to me to separate the acontia-lacking Athenaria, provided with a mesogloeal sphincter from the other forms, 

 and to place them in a separate family, Halcampidae. Thus I cannot adopt the classification neither of Me. 

 Murrich nor of Poche, who do not see any reason in the character of the sphincter for the formation of a 

 family Halcampidae, based on the occurrence of a mesogloeal sphincter. Besides, how inconsistent Poche 

 is in keeping the family Ilyanthidae, based on the occurrence of a diffus-circumscript endodermal sphincter, 

 while he separates the two with acontia provided families, Andwakiidae and Halcampactiniidae, though 

 the only difference between these latter consists in the former having a mesogloeal sphincter, the latter none. 

 The family Halcampidae, based on the presence of a mesogloeal sphincter, must therefore be maintained. 



Concerning the family Ilyanthidae s. str., it might possibly be placed together with some of the re- 

 maining forms (the family Halcampoididae), as forms with an endodermal sphincter are rather to be referred 

 to forms with no sphincter. I do, however, think that it is more practical to keep this family. 



To the family Peachiidae (Siphonactiniidae) the genera Peachia, Eloactis and Haloclava are referred. 

 The characters on which the family might be based are as follows: i) the bilateral arrangement of the 20 



1 According to several authors the genus Aiplasia has no sphincter or is provided with now an endodermal, now a mesogloeal 

 one. For the species with a mesogloeal sphincter Stephenson (1918 p. 51) has proposed a special genus Aiptasioides with the species 

 prima and pallida which he refers to the subfamily Metridinae. Though I have no particular knowledge of these genera, I would be 

 inclined to go still further and place the genus Aiptasia in a special family Aiptasiidae. The whole family Sagartiidae besides needs 

 a radical revision, some species of Phellia probably belong to the Andwakiidae. 



Since this paper was written, Stephenson in a paper (1920 Quart. Journ. Mic. Sc. 64) has divided the Sagartians into several 

 families. I agree with him that the Sagartians are not a homogeneous group, and with Bourne (Quart. Journ. Mic. Sc. 63, 1919) that 

 they are of different origin. In the second part of this work I will further discuss this question. 



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