PORIFERA. I. 



spongiii is either not seen to surronnd the fibres at all, or onh' to surround them to a slight degree, but 

 most frequently the spicules form the middle part of the fibres and are enclosed b\- a strong sheath 

 of spongin. In the transverse fibres the spicules are fewer and often not so regularly arranged after the 

 longitudinal axis, as they are in the longitudinal fibres, but there is plenty of spongin. In the stalk 

 the spongin is particularly copious, and therefore the consistenc)' is harder than in the other parts of 

 the sponge. The fibres form a rather regular skeleton; from the base and middle of the sponge the 

 longitudinal fibres, the primary ones, spread, in a sheaflike way, on ever>' side upward and bend to- 

 wards the surface, in some places branching off in acute angles; perpendicularh- on those the tran.s- 

 verse fibres are found, which only stretch from one longitudinal fibre to the next one without forming 

 longer coherent fibres; neither are they present in any great number, and accordingly in most places 

 the}' are far from each other, so that the meshes formed get a rectangular shape; only at the surface 

 are the transverse fibres closer together, and here the meshes become quadratic; iunnediately at the 

 surface the transverse fibres form a dense, but irregular net of meshes on which the dermal membrane 

 is resting. Farther down in the sponge may be found the la\ers mentioned in the introduction to 

 the ChaliiiUicr, running more or less parallel with the surface, and with more closely set transverse 

 fibres, so that these layers remind of the structure of the surface of the skeleton. This peculiarity 

 must be connected with periodicity in the growth. The distance between the longitudinal fibres 

 generally varies from o^™"' to 0'6"'"\ On account of the above mentioned structure of the skeleton it 

 will in the middle part of the more or less cyliudric sponge show a rather irregular texture, from 

 which longitudinal fibres radiate on every side running upward and bending outward to the surface. 

 This structure of the skeleton is distinctly seen as well in a transverse section as in a longitudinal 

 one through the middle of the sponge. 



Spiciila are oxea slighth' curved and \-er}- gradually tapering; the tapering is so gradual, that 

 the thickness decreases from the very middle of the spicide; but the decreasing in thickness is not 

 great, so that tlie point proper commouh- is not especialh- long. The length is between o'ljS""" and 

 o-2o8'""\ and the thickness in the middle varies between ca. o'Oi"'"' and o'oi4"™'. Among the oxea some 

 styli are seen which are almost always short, and are to be regarded as monstrous forms. Some 

 needles a little shorter and especially finer, up to very fine ones, are seen, which I take to be deve- 

 lopmental forms; they are, however, seen in the fibres, and fibres exclusiveh" filled with such needles 

 may be found. 



It has not been possible to refer this species to any one hitherto described; among species that 

 had to be taken into consideration, were especially Pachychalina compi'essa Schmidt and P. excelsa 

 Schmidt. Both these species have been mentioned so briefl}- that it woidd be impossible to recognize 

 them, but the original .specimens of both species are in the museum of Copenhagen. P. compressa 

 was founded by Schmidt 1870 (Grundziige einer Spongieufauna d. atlant. Gebiet p. 37) as occuring at 

 Iceland; an examination of the original specimen, however, has now pro\ed it to be, not a Pachycha- 

 lina but a Homceodiciya, the chelse so characteristic for this genus having been found in it, although 

 in small numbers')- The other species was founded by Schmidt in the same place as occurring at 



') I must here call attention to the fact tliat the Chalinince and the genus Hommodictya, which latter, at all events 

 some of its species, as to skeleton and outer form is verv like the former, maj- easily be confounded when the specimens 



