PORIFERA. II. 3 



and Isochelse--, and in which therefore a thorough examination of these features might be expected, 

 we find nevertheless that on PI. II, fig. 9, and especially fig. 11, which latter represents an almost grown 

 (rather a quite grown) chela, no tooth has been drawn in the smaller end. Also in Topsent's other- 

 wise excellent works too little attention has been paid to the study of the chelae; in his work from 



1892 (Resultats des Campagn. scient. du Prince de Monaco, Fasc. II) the chelae are shown in very small 

 figures, aud most frequently the tooth has not been figured. In the work on the sponges of the 

 Belgic Antarctic Expedition from 1902 (Voyage du S. Y. Belgica, Spongiaires) the case is somewhat 

 similar; thus the tooth is not drawn on the chela seen from the front, PI. Ill, fig. 9 b. Even in the fine 

 work from 1904 (Resultats des Campagn. scient. du Prince de Monaco, Fasc. XXV) errors of this kind 

 are found; thus the chela; on PI. XIV, fig. 15 e, fig. 18 d, and PI. XV, fig. 20, are drawn without the 

 tooth, while others, especially the larger ones, are drawn correctly. 



As mentioned above, all these forms are generally comprised under the name of cheke, and 

 are regarded as being principally of the same kind. In contradistinction to this view Levin sen in 



1893 (Vidensk. Medd. fra den Nat. For. Kobenhavn 1893, 1) has advanced a new view, dividing these 

 bodies into two principally different forms and giving to these the respective names of chelae and 

 ancorae. The difference between these two forms is briefly, that chelae have only one free tooth and 

 besides more or less broad lateral alae on the shaft, while ancorae have more, 3 — 7 free, uniform teeth 

 besides lateral alae on the shaft. Levinsen regards the teeth in both forms as bendings of the axis. 

 Carter and Ridley aud Dendy regard the lateral teeth in aucorte and the alae in chelae as formations 

 of the same kind, and are most inclined to regard the lateral teeth in ancorae as developed by the 

 alae of a chela being split of from the shaft. Vosmaer and Pekelharing in the above quoted paper 

 from 1898 attack the interpretation of Levinsen, and declare that the teeth of the ancorae cannot be 

 interpreted as bendings of the axis, as long as an axial canal has not been made out in all the teeth 

 of the ancorae, and if these teeth are formed by the axis being bent and split in several branches, 

 then a sponge with such spicules would not belong to the Monaxonidae. The authors think it most 

 probable that the ancorae have arisen by a splitting of the tooth of the chela. 



To these different theories it is only to be remarked that it may be regarded as a fact that 

 chelae and ancorae are allied bodies, but that it cannot at present be decided, in what way one form 

 may be thought to have arisen from the other. Now it is certain that in a few chelae we may meet 

 with a feature which is probably a splitting of the tooth, as in some Asbrs/oJ>lu///a-species in the 

 smaller end of the chela, and in the present work in the genus Myxilla instances will be shown of 

 ancorae with at all events a beginning splitting of teeth; but at present it is impossible to decide how 

 this fact is to be interpreted. On the other hand it is certain that the two forms, as they now occur, 

 are principally different: in one form, chelae, only one tooth is found and alae on the shaft, in the 

 other form, ancorae, several quite homologous teeth are always found as well as alae on the shaft. 

 Transitional forms have not been found hitherto, and when Ridley and Dendy say (Challeng. Rep. 

 Monaxonida, XIX): Numberless gradations exist between these two types , this is not correct; their 

 view arises from the fact, that they put ancorae and chelae arcuatae together in one group in contra- 

 distinction to chelae palmatae, but even from this point of view the statement is not correct. The 

 objection of Vosmaer and Pekelharing, that the ancorae, if the representation of Levinsen is 



