from the North Sea. 85 



they consist of spindle-shaped needles, of exactly the same 

 type as those of the stem, but smaller. Ten measurements have 

 given from 1*14 millim. in length and 0*013 millim. in thick- 

 ness to 0*4 millim. in length and 0*011 millim. in thickness ; 

 the mean length was 0*73 millim., and the relation of length 

 to thickness in one aa 100 : 2*86, in another as 100 : 1*09, the 

 mean of twelve measurements being 100 : 1*85. Very rarely 

 there appear some few small straight needles without nodules 

 near the middle (fig. 27). The nearer the surface, the more 

 the bundles divide ; but, regularly, not one of their spicules 

 reaches out of the dermal layer, in which appear other 

 spicules (fig. 34) of the same type as those in the skin of the 

 stem, but longer, arcuated, Avithout nodule (fig. 35), and 

 placed in the same manner. The measurements gave from 

 0*45 millim. in length and 0*004 millim. in thickness to 0*34 

 millim. in length and 0*0046 millim. in thickness ; the mean 

 length was 0*39 millim. ; the relation of length to thickness 

 in one as 100 : 1*25, in another as 100 : 0*8, the mean being 

 100:1. 



The interstices between these bundles of spicules, which 

 form the partitions of the canal-system of the head, are filled 

 with the parenchyma, which, although it has been a very long 

 time under the influence of the alcohol, has a yellowish-brown 

 colour, is firm and tough, has very numerous, mostly oblong 

 corpuscles and granules, among which there are some larger 

 ones with granular contents (fig. 3G). 



From the rather thickened base of the stem, out of its 

 dermal layer, a great number of roots go ofi", irregular and 

 branched filaments here and there forming loops and gradually 

 spreading over a surface almost twice as great as the upper 

 surface of the head (fig. 37). The roots consist in greater 

 part of a tolerably transparent colourless substance, the same 

 as that of the skin, covered by a somewhat thin layer of fine, 

 yellowish, granular matter. Very rare, extremely small and 

 straight spicules may possibly belong to this layer, though it 

 is very difficult to refer them to it with certainty among the 

 great number of foreign objects of many kinds which are 

 attached by the granular layer's having crept over them and 

 penetrated even into the canal of the fragments of sponge- 

 spicules (fig. 38). 



When the stem of the sponge is broken not far from the 

 root, and the upper part, thus separated from the basal, is 

 turned upside down and placed on the flattened surface of the 

 head, the stump of the stem directed upwards, it has an un- 

 questionable likeness to the well-known Hyahnema Sieboldi^ 

 Gray, as this has been hitherto exhibited. AVhat we have 



