PORIFERA. III. 



I0 3 



upwards on the head, and they may here vary somewhat in length. The size of the styli varies 

 somewhat, but there are no groups; the length is 0-083 o-22 mm and the diameter of the head is 0-012 

 0-02 mm . The size may be somewhat different in various individuals, the styli sometimes not reaching 

 over o-i5 mm in length. 2. The dermal spicules are subtylota varying to strongyla; they are straight 

 and slender; when they are of tylote shape one end of the shaft is thinner than the other, and this 

 thinner end has a distinct end-swelling, while the other end is more evenly and but slightly thickened; 

 the shaft is generally of the same thickness in the whole length, but sometimes somewhat thickened 

 in the middle. The length of the dermal spicules varies in all from 0-149 0-28 mm , and the diameter 

 from 0-002 0-005""", btit the difference is not so great in the single specimens, as these spicules may- 

 vary to a rather considerable degree in different specimens; thus the following measurements were 

 taken from different specimens: 0-149 o-ig"" 11 , ' 1 ^ O'2o mm , 0-19 0-24 mm , 0-18 o-28 mm and 0-20 0-28 mm . 

 Very often the larger spicules are strongyla or slightly tylote, while the smaller are more distinct 

 tylota. Microsclera are not present. 



Embryos. In many of the specimens embryos were found. They are globular and of an average 

 diameter of 0-23"""; they are often present in great numbers. Nearly all the specimens examined had 

 spicules, only a single one without spicules was seen. The spicules are styli considerably smaller 

 than those of the grown sponge; they were measured from 0-028 0-078 mm in length and from exceedingly 

 fine to 0-008 rara in diameter at the head; otherwise they are acanthostyli chiefly of the same shape as 

 in the grown sponge, only the spines are less developed, in such a way, that the spicules may be 

 termed coarsely and rather densely gritty. 



It will thus be seen, that the spicules first appearing in the embryo are the skeletal spicules; 

 this was also to be expected, the same being the case in the Myxilleae, as I have shown in the second 

 part of this work in several instances, in the genera Myxilla, lophon and Forcepia, in the embryos of 

 which the skeletal spicules are also the megasclera first appearing. Topsent declares on the contrary 

 (1. c. 1888, no), just with regard to the present species, that the first developed spicules are the dermal, 

 and he says further that this also holds good with regard to Myxilla incrustans. It is somewhat 

 strange to me how he has got to this result; I can only imagine that he has examined embryos with 

 very young and fine spicules, in which case these may perhaps be mistaken for dermal spicules. 



Locality: This species has been collected in rather great numbers; station i, 62 30' Lat N., 

 8 2 1' Long. W., depth. 132 fathoms; station 6, 63 43' Lat. N., 14 34' Long. W., depth 90 fathoms; station 

 25, 63 30' Lat N., 54 25' Long. W., depth 582 fathoms; station 27, 64 54' Lat N., 55 10' Long. W., depth 

 393 fathoms; station 28, 65 14' Lat. N., 55 42' Long. W., depth 420 fathoms; station 35, 65 16' Lat N., 

 55 05' Long. W., depth 362 fathoms; further it has been taken at East Greenland, Forsblads Fjord, 

 depth 5090 fathoms (The Amdrup-Expedition 1900), and at the Faroe Islands, depth 30 fathoms (Th. 

 Mortensen). The localities are situated in the Davis Strait, at East Greenland, the Eastern coast of 

 Iceland and the Faroe Islands. 



Geogr. distr. H. Dujardinii was hitherto recorded from the Eastern coasts of Britain and Ire- 

 land (Bowerbank); from the French coast of the Channel (Luc, Roscoff, Calvados) (Topsent), the Bay 

 of Gascogne, depth 95 fathoms (Topsent), the coast of Provence at Ciotat (Topsent), at the Azores in 

 depths of 69 and 28 fathoms, at 46 47' Lat. N., 60 12' Long. W., depth 72 fathoms (Topsent), finally at 



