Porifera. 



II. 



By 



William Lundbeck. 



THE present work, as shown by the title, is a direct continuation of my work, « Porifera, Part I, 

 The Danish Ingolf-Expedition, VI, i, published in 1902. In the introduction to this first part I 

 rendered an account of the material and of the geographical territory treated in the work. Since that 

 time some new material from the territory has been added, and this material has been included in 

 the work. The new material has especially been gathered by the surveying vessels the «Diaua» and 

 Beskytteren > stationed at Iceland and the Faroe Islands, on the cruise of the «Thor», the steamer of 

 the international investigation of the sea, in 1903 under the direction of Dr. Joh. Schmidt, aud more 

 particularly must be mentioned the very considerable material collected by Dr. A. Appellof and 

 cand. mag. Ad. Jensen during the cruise of the Michael Sars in 1902 under the direction of 

 Dr. Hjort. 



In the first part of the work the families Homorrhaphida and HetcrorrhaphidcE of the sub-order 

 Haliclwndrince were treated. The present part comprises part of the family. Desmacidonidce. Partly 

 tollowing Topsent I divide this family into the subfamilies Mycalincc (= Esperellince olim) and Ecty- 

 onincB; Mycalinm I divide into two groups Mycalea and Myxillea (the latter corresponding to the 

 subfamily Dendoricinm of Topsent). I regard these two divisions as groups of one subfamily, as I 

 think them more closely allied to each other than to Ectyonina, at all events when the question is 

 of the typical forms of this sub-family. On the other hand, several genera of EctyonincB are assuredly 

 closely allied to genera of the group Myxillecv. The systematism of the sponges is still in main- 

 respects groping its way, aud such is also the fact inside the family Desmacidonidce. The separation 

 into the two subfamilies Mycalincr and EctyonincB is scarcely a quite natural one, in the way in which 

 it is made at present, being chiefly based on the occurrence of special, socalled accessory spicules in 

 the latter subfamily. Thus the dermal spicules with equal ends characteristic of the Myxillcce, occur 

 also in some Ectyo/u'ncz-genera; the accessory acanthostyles are often very scarce, or the acanthostyles 

 of the species are so very varying in size, that it is difficult to decide whether two separate groups 

 of sizes are present. The decision is especially difficult in incrusting forms, where the character of 

 the accessory styles jutting out from the fibres is wanting, all the styles being basal. A particular 

 fact is also the occurrence of parallel, corresponding genera in the two subfamilies; thus Myxilla (--= 



The Ingolf-Expedition. VI. 2. I 



