z . PORIFERA. II. 



able partlv to assume a free, branched form, as stated by Levin sen I.e. The specimen of Levin sen, 

 however, has incrusted a Hydroid, and presumably its form is partly owing to this fact; but the speci- 

 men has also free branches, in which nothing of the Hydroid seems to be found, as also the primary 

 fibres of the branches may be found running longitudinally, while, if the question was of a cover, 

 thev would have to be supposed to run from the middle, from the body incrusted, perpendicularly on 

 the surface. The largest specimen in hand has a greatest extent of ca. 75 mrc . The colour (inspirit) is light 

 yellowish. The consistent is rather loose and soft. The dermal membrane is thin and transparent 

 without spicules; it is supported by the skeleton below and pierced by the ends ol the fibres, conse- 

 quently the stir/ace is finely shaggy. On account of the apertures of the incurrent canals shining 

 through, the surface gets the netlike appearance, as is found, for instance, in most Re ///era-species. 

 The fores are very close-set in the dermal membrane, so that it is reduced to a network; they are 

 round and of an average size of 0-05 — cri 1 ""'. Oscula are scattered on the surface; they have generally 

 a diameter of from a little more than one to 3""" ; they are situated on the top of more or less marked, 

 but always low, flatly conical projections. 



The skeleton is of a renierid structure. It consists of fibres running from the base towards 

 the surface where they pierce the dermal membrane. These fibres are polyspicular, and they have 

 generally, as stated by Bower bank and Levin sen, about three spicules in breadth; sometimes also 

 a little more. The transverse fibres are almost always only represented by single spicules, they form 

 no coherent fibres, and they are situated very irregularly. The distance between the primary fibres is 

 on an average ca. o-i5 mm . In the deeper layers of the sponge the skeleton is irregular, and here no 

 distinction can be made between primary and secondary fibres. Spongiu is found in the skeleton, 

 especially distinctly in the nodes, but it is white and exceedingly clear, and therefore not easily 

 observed. 



Spicula: a. Megasclera are somewhat curved styli; most frequently the curve is even, only 

 rarely it is a little sharp; it is generally found in the middle, sometimes nearer to the head-end; the 

 opposite end is evenly and rather long tapering. They are somewhat varying in length, partly in 

 one individual, and partly in different individuals; upon the whole the length of the styli in the 

 specimens in hand is between 0-16 and o-25 mm . Also the thickness is varying, and is between ca. 

 0-0057— o-oii4 mmI ). Such is the thickness of the spicules that seem to be fullgrown, but developmental 

 forms of every thickness down to quite fine ones are also found; they are only very little shorter 

 than the fullgrown ones. b. Microsclera; these are only found of one kind viz. isochelae palmatse; 

 they are a little curved, but the middle part of the shaft, between the alae of the two ends, is straight 

 or sometimes slightly curved inwardly; this middle part is about one third of the length. The tooth 

 is of about the same length as the alee, and its breadth is like that of the alse taken together. On 

 the sides the tooth and the alse bend towards each other, but when the chela is viewed from the side 

 these recurvings, on account of their fineness, are almost not to be distinguished. The length of the 

 chelse is 0-020— 0-021 mm , and their breadth is ca. 0-0057"™. Of tne chelae developmental forms are found; 

 the youngest one observed appears as a thin staff -with rather long recurvings in both ends, without 



') In some specimens the needles have an average length of 0-23— 0-25""" with an average thickness of o-oimm; in 

 others the length is on an average 0-17 — o-2o'» m with a thickness of o-oo7 mm . 



