i6 



PORIFERA. I. 



copious in all the nodes, and in the priman- fibres it may frequenth- be seen to surround the spicules 

 completely, while the transverse spicules most frequently appear to be onl\- cemented at the ends. 



Spicula are rather small oxea; they are always more or less curved; sometimes the cur\-e is 

 even, but frequently it is more sharplj* localized in the middle of the spicule. The pointing varies 

 somewhat, from a fairly long to a quite short, sometimes even rounded point; in the latter case the 

 rounding has a quite small point marked off. The length \aries from 0-13— o- 178""", most frequently 

 towards the latter figure, also the thickness is somewhat varying from o'OoS— o-oii"'"". The thickness 

 and length are in no fixed proportion to each other. Shorter and finer needles, up to exceedingly 

 fine ones are found in no small number spread in the tissue, the shortest ones measured had a 

 length of o-oga""". 



Locality. Egedesminde, Greenland, depth unknown, one specimen (Levinsen). 



^j Subfam. 2. Renierinae. 



.7 



Halichondria Heming. 



Without definite form, fanning incrustations, lumpy or more or less erect. The needles zoiihout 

 any real order spread in the tissue, sometimes forming fibres, but no regular reticulate skeleton. 

 Spicula oxea, commonly long and slender, rarely strongyla. Spongiti zvantitig (or present only to a 

 scarcely appreciable amount). 



The sponges belonging to the genus Halichondi'ia are usually of no definite form. The\' mav 

 form incrustations, be formed as thicker or thinner crusts, or be irregularly massi\-e or lump\', or the}' 

 ma\- finally be more or less erect and sometimes slightly branched, and it is to be supposed that 

 several species may appear under more or less of these various forms, or at all event vary much in 

 form, and these variations ma\' even to a certain degree influence the other structure (the skin, the 

 skeleton 1. The recognition of the species must therefore primarily be done by means of the spicules, 

 and the other skeletal structures, the nature of the surface etc. can only be of secondary importance. 

 In spite of the general recognition of the secondary importance of the outer form, not onh- here, but 

 upon the whole in many Monaxonids'), there has not uncommoul)- been laid too much stress upon 

 this feature. The species of the earlier authors will, when no exact figures and measures of the needles 

 are given, commonly not be identifiable. Bowerbank thus under the genera Hymeniacidon and 

 Halichondria has twenty and odd species belonging to the genus Halichondria in the signification 

 used in this work; this, no doubt, is too large a number, but most of these species will not be iden- 

 tifiable without an examination of the original specimens. 



'J It is to be supposed, however, that the secondary importance of the outer form applies especially to the genus 

 Halichondria (and a few other genera, for inst. Hymeniacidon), and is connected with the only little differentiated skeleton of 

 this genus; it is also seen that species of this genus, when they have a skeleton made of fibres, get a more definite form. 

 Ifaliclioitdyia paiiicea is a good type of an especially varying and polymorphous species. The outer form of the sponge species, 

 however, is often little known, because many species have been etablished on slight material, fragments or more or less 

 damaged specimens. I am inclined to think that it will be seen by and b_\-, when new collections procure well-kept specimens, 

 that the species often, within certain limits, have a rather definite form. 



