24 



PORIFERA. III. 



layer; spongin is also present in the dermal membrane, and on examination the membrane gives the 

 impression of being quite or partly a spongin-lamella; the spongin of the skeletal fibres continues 

 directly over into the membrane. It is this consistency of the membrane about which Carter uses 

 the expression "a horny sarcodic membrane". In the membrane there are found fine thickenings or 

 slightly elevated lists running circularly round the sponge, they seem to be thickenings of the spongin, 

 and are possibly phenomena of growth. 



Spicula: a. Megasclera are somewhat curved strongyla, they are thickest in the middle and 

 taper towards the ends, more towards one end than towards the other, and they are thus unequal-ended. 

 The ends are quite slightly spinulous outermost on the rounded part, sometimes they may be smooth. 

 The length is 0-32 — 0*536 mm and the thickness is 0-017— o - 022 mm . Some finer to quite fine develop- 

 mental stages were seen, the finest are monactinal and thus show that these unequally-ended strongyles 

 originate from styles, b. Microsclera ; these are of two forms, isochelse palmatse and toxae. 1. The 

 chelse palmatse are very small and of the typical shape, the tooth is of the same length as the 

 alee and of the same breadth as these together; the alse seem to be only very slightly refolded 

 laterally so far as I could see under a high magnifying power (x 1400). The length is 0-014 — 0-017 ran ' 

 and the breadth about o-oo28 mm . 2. The toxa are long and fine, the curvature is most frequently 

 very slight; sometimes they are only curved in the middle, but most frequently also the end parts 

 are slightly recurved; sometimes they may be somewhat irregular, so that their shape as toxa is not 

 distinct; they are of the same thickness in the whole length, only the ends are finely pointed. The 

 length is o - 2i — o-30 mm and the thickness about o-ooi6 mm . Carter mentions and figures as "subskeleton 

 spicules" some fine spicules, which he terms "acuate", but his figure shows two, of which one is a style, 

 the other pointed at both ends; it is presumably a confusion of developmental stages of the strongyles 

 and toxa which forms his "subskeleton spicules". I have not seen toxa quite so strongly curved as 

 shown by Carter's figure, but no doubt they may vary a good deal in curvature. The microsclera 

 occur everywhere in the soft tissue of the sponge, the chelse are present in very great numbers. 



Embryos. In one of the specimens an embryo was found; it was situated about in the middle 

 of the sponge and had a size of about o-6 mm . It contained numerous megascleres, but there seemed 

 to be no microscleres present. The megascleres are similar to those in the grown sponge, only con- 

 siderably smaller, of a length of about o-20"' m . 



Locality: Station 4, 64 07' Lat. N., n° 12' Long. W., depth 237 fathoms; station 143, 62 58'Lat. N., 

 7 09' Long. W., depth 388 fathoms, (bottom temperature -*-o°4C); further it has been taken at 62 40' 

 Lat. N., i° 56' Long. W., depth 365 fathoms (bottom temperature -=- o° 3 C), 62 29' Lat. N., 4 12' Long. W., 

 depth 283 fathoms (Ad. Jensen, the cruise of vl M. Sars" 1902); finally it has been taken at East-Green- 

 land, 74 17' Lat. N., 1 5 20' Long. W., depth 127 fathoms (The East-Greenland Exp. 1891—92). Five 

 specimens or fragments in all. 



Geogr. distr. The species was earlier taken on the "Porcupine" Expedition, 6i° 10' Lat. N., 2° 21' 

 Long. W., depth 345 fathoms (bottom temperature -*- i° 1 C) (Carter 1. a), and in the Baffin Bay, 72 32' 

 Lat. N., 56 05' Long. W., depth 116 fathoms. The species is accordingly distributed between 1° 56' and 

 56 05' Long. W., and between 61° 10' and 74 17' Lat. N., in the Baffin Bay, at East-Greenland and 

 around the Faroe Islands. The depths are from 116—388 fathoms. The species presumably belongs 



