PORIFERA. III. 



being for a great part spined oxea. The skeleton of the fistulae is also here arranged ring-like, but 

 outwards it soon becomes more irregular and scattered; fibres running through the fistulse in longi- 

 tudinal direction are not found here, or they are at all events only very little pronounced and soon 

 dissolved into spicules lying more scattered in the longitudinal direction. The skeleton of the inner 

 body is constructed quite as in H. appcndicidatum; there are fine, parallel fibres running along the 

 surface and without connecting transverse fibres, and they run together at the bases of the fistulse, 

 some of them may continue out in the fistulse; in the interior of the inner body similar fibres are 

 found, but they are scattered without observable order; besides there is found a number of single, 

 scattered spicules, which for a great part are spined oxea. Spongin could not be observed in the 

 skeleton. 



Spicula: a. Megasclera; these are of two forms, tylota and acanthoxea. i. The tylota are 

 straight or slightly curved, they have a well developed swelling at either end, the shaft is thickest in 

 the middle. The length varies much, from 0-29 0-65 mm , with a diameter of the shaft relatively of 

 0-007 0-017 mm . Some developmental stages are found down to quite fine, the thinnest of them are 

 monactinal, the older show one end rounded or slightly swollen, while the other end has a pointed 

 swelling which represents the original apex, and the shaft is thinnest at this end. There is no differ- 

 ence between the tylotes in the dermal layer and those in the inner body, but the developmental 

 stages are found in the interior. 2. The spined oxea or acanthoxea are curious and characteristic 

 spicules; they are straight or quite slightly curved, and relatively short and thick, the points are 

 middle-long and sharp; the spicule is coarsely spined in the whole length, only the points are smooth 

 to a greater or smaller extent. The length varies from 0-17 o-2i mm and the diameter from 0-008 

 0-014. Some single developmental stages were seen, the thinnest of them slightly spined, these 

 had a thickness of 0-004 mm . The tylotes form the dermal layer and the fibres in the inner body 

 are also found scattered singly in the interior; the spined oxea are seen scattered singly in the dermal 

 layer, but are for the rest present, as said, on the inner side of the layer, lying at right angles 

 to the other spicules, further they are found scattered in the inner body. b. Microsclera ; these 

 are of two forms, chelae arcuatse and sigmata. i. The chelse are somewhat small, they have a 

 slightly curved shaft, the alse are incised below and drawn out in a point, the tooth is narrow. The 

 length is 0-021 o-o28 mra , and the thickness of the shaft about 0-002 mm . Chelae of somewhat deformed 

 shape were not infrequent. 2. The sigmata are rather fine, they are contorted generally about a 

 quarter of a turn; the length is 0-056 o-o6i m and the thickness 0-002 0-0028 mm . The microscleres 

 occur on the inside of the dermal layer and in the inner body, but they are on the whole not numerous. 



"Cellules spheruleuses" . In this species the so-called cellules spheruleuses occur, often in 

 enormous numbers; they occur especially on the inside of the dermal layer and the fistulse and in the 

 inner body, chiefly at the surface of the latter. They are roundish or more elongate and filled with 

 relatively large, refracting granules; their size is generally o-oii 0-017 mm . Sometimes they are some- 

 what confluent to larger heaps of granules. 



Locality: The species has only been taken on station 78, 60 37' Lat. N., 27 52' Long. W., depth 

 799 fathoms, on the eastern slope of the Reykjana;s Ridge; a somewhat large number of specimens. 



