PORIFERA. II. 67 



are shaggy from projecting spicules. On the stalk and the branches only a very thin layer of tissue 

 is seen; on the thickened part between the bases of the branches, on the other hand, tliere is a thicker 

 layer of tissue, which is bounded outwardly by a dermal membrane, supported by no particular skeleton, 

 but provided only with microscleres. Pores and oscula were not seen. 



The skeleton. In the stalk the skeleton consists of needles closely united and parallel to the 

 longitudinal axis. The spicula-axis formed in this way divides above into a number of more or less 

 distinctly separated fibres bending a little outward, and between these fibres those of the branches 

 are inserted. These latter fibres also consist of closely united, parallel spicules. As will be more par- 

 ticularly mentioned below, the spicules of the stalk are thicker and more fusiform, those of the branches 

 more slender and less fusiform. In the stalk a rather slight amount of very clear spongin is found. 



Spicnla: a. Megasclera are subtylostyli of two- forms, those of the stalk and those of the 

 branches. The subtylostyli of the stalk are straight, rather thick, and highly fusiform, tapering much 

 towards the head-end; the tapering may otherwise be somewhat varying. They have a head-swelling 

 which is most frequently inconsiderable, and almost always placed a little below the end. The oppo- 

 site end tapers from the middle evenly towards the point, but the end itself is somewhat more abruptly 

 pointed, especially in the thicker ones. The length is rather varying, from 0-47 — o-8 mm , and the thickness 

 from 0-017— o - 028 mm , the thickest ones being far from always the longest ones. The spicules of the 

 branches are likewise straight, or very slightly curved, fusiform subtylostyli, but they are somewhat 

 slenderer than those of the stalk, and so they are not so markedly fusiform as those. The swelling 

 of the head-end is a little more pronounced, and is also here placed a little below the end. The 

 opposite end is long and evenly tapering. Their length varies between 0-35 — o-6 mra , and the thickness 

 varies proportionately between o-oo6— o-oi4 mra . As mentioned above the larger spicules form the skeleton 

 of the stalk, and the smaller ones that of the branches, which is formed exclusively by these latter, 

 but they may also be found in small number in the periphery of the stalk, and the spicules projecting 

 in the lower part of the stalk are of this form. Thus the two forms of spicules have each of them a 

 special place of occurrence, and they show also so much difference as to form, that they may generally 

 be referred at once to their separate group. It is, however, scarcely to be supposed that they form 

 two fundamentally different forms, as transitions are found between them, and these transitional forms 

 occur exactly at the place where the stalk and the branches pass into each other. Here, in the thick- 

 ened part, from which the branches issue, transitional forms are found that may be referred to one 

 form as well as to the other. The basal expansion is formed by both kinds of spicules, the prominent 

 ones seem chiefly to belong to the smaller form; but here again the two forms are not sharply 

 separated, but transitional forms occur, b. Microsclera; these are of one kind only, anisochelse 

 ■palmatEe of the Lycopodi/m-type; they have a form quite similar to that of the chelae in the two 

 preceding species, but they are a little smaller, the length is 0-012— o-oi4 m,n , most frequently, however, 

 the latter length; the breadth is o-oo5 mm . The chelae, as usual, occur throughout the tissue, but are 

 especially numerous in the dermal membrane. 



Locality: Of this small, interesting, and beautiful species, which is easily recognizable by its 

 outer form alone, the Ingolf-Expedition has obtained fifteen specimens in all; most of them were not 

 found till after the return of the Expedition, when they were discovered in the bottom specimens 



9* 



