j - 2 PORIFERA. II. 



polyspicular, and the thicker ones have many spicules alongside. The first and thickest fibres issuing 

 from the stalk have an average thickness of o-6 ram , and the thinnest branches going to the surface are 

 ca. 0'05 mm thick. Spongin is found in the fibres through their whole length, coating them, perhaps, 

 with an exceedingly fine layer, but it is white and clear and not easily observed; it is most copious 

 in the stalk. 



Spicula: a. Megasclera. i. The skeletal spicules are smooth styli; they are slightly curved, 

 and the curve is generally situated nearest to the head-end. They taper quite imperceptibly towards 

 the head-end; towards the point they are somewhat tapering, but the point itself is short. Their 

 length is between 0-39 and o-63 mm , and the thickness is 0-012 — o-oi6 mra ; the longest ones are not always 

 the thickest ones. In the basal expansion and in the stalk the styli, as mentioned, are considerably 

 shorter, only 0-208 — 0-35"™; upward in the stalk they become gradually longer, and in the upper part 

 of the stalk they reach o - 47 mm . 2. The dermal spicules are tornota; they are straight, or slightly, 

 and then frequently a little irregularly, curved. Their ends are most frequently slightly swollen, they 

 are about rounded and end with a little mucro. The ends are not quite equal, one being a little 

 thinner than the other and generally a little more pointed. Their length is 0-31— 0'488 ram , and the 

 thickness 0-0067 — o-oio min . b. Alicrosclcra ; these are only of one form, chelae arcuatse. They have a 

 somewhat curved shaft, the lower edge of the alae are only little indented, and therefore the ala is 

 not much tooth-shaped; the tooth is narrowly elliptical, of the same length as the alee, and there is a 

 small tuberculum broadest downward. The chela must be called arcuate, but it forms a transition to 

 the palmate ones. The length is 0-032 — o - 045 mm , the thickness of the shaft is ca. 0-003— o-oo5 mm ; the 

 shaft is not cylindrical, but more or less compressed. A few developmental forms were seen as thin 

 staves recurved at both ends. The chelae occur through the whole sponge, but they are especially 

 numerous in the dermal membrane. 



Embryos. In most specimens embryos were found copiously scattered in the tissue. They are 

 globular or a little flattened, of a diameter of up to 0-48"""; on account of their white colour they 

 were easily discerned in the tissue. No spicules were found in them. 



Locality: Station 10, 64 24' Lat. N., 28° 50' Long. W., depth 788 fathoms (bottom temperature 

 3°5 C), two, mostly denuded, skeletons ; station 104, 66° 23' Lat N., 7° 25' Long. W., depth 975 fathoms 

 (bottom temperature -=- i°i C), one large and two small specimens; station 105, 65 34' Lat. N., 7 31' 

 Long. W., depth 762 fathoms (bottom temperature -=- o°8 C), four specimens; 62 30' Lat. N., i° 56' Long. E., 

 depth 275 fathoms (bottom temperature negative), a small specimen (Ad. Jensen, the cruise of the 

 <Michael Sars> 1902). As is seen from the list, the three localities are from the cold bottom, and 

 according to this the species must be supposed to be a native of the cold area; the fourth locality, 

 station 10, on the contrary, is situated on the south side of the ridge between Iceland and Greenland, 

 and it is positive. Now it is to be remarked, however, that from this locality we have only two almost 

 quite denuded skeletons, and so there is a possibility that these specimens have been dead, and have 

 been carried to this locality as dead. This is also indicated by another fact; all the other specimens 

 with the exception of a few ones that have been broken off, are attached to the stone which serves 

 for their attachment, whereas the two specimens from station 10, although they have the basal expan- 

 sion of the stalk undamaged, are loosened from their substrata. 



