BY E. F. KALLMANN. 373^ 



with occasional branching and anastomosis, in a general surfaee- 

 ward-direction ; the connecting fibres, which vary from unispieular 

 to rarely multispicular, occur at rather variable intervals, and, 

 where the main fibres are more widely separated, from between 

 them an irregular inter-reticulation. As the surface is nearly 

 approached, the connecting fibres disappear, and the outwardly- 

 running fibres become split up into numerous closely-arranged 

 and parallel strands of loosely-associated tylota, ending at the sur- 

 . face, each in a slightly penicillate tuft ; in the dermal skeleton thus 

 constituted, there occur in addition to the vertically arranged spic- 

 ule-strands only a very few scattered raphides. In places — though 

 this seems to be exceptional — the dermal skeleton, while otherwise 

 unchanged in character, appears not to be in continuity with the 

 main skeleton. The extent to which spongin is developed in con- 

 nection wath the fibres, varies considerably in different parts; fre- 

 quently it forms a quite conspicuous sheath which, in thickness, 

 may exceed the diameter of the spicule-core, the fibre as a conse- 

 quence attaining sometimes to a stoutness of iOfi or more ; usually, 

 however, it is barely more than sufficient to hold the spicules to- 

 gether ; while towards the surface, it further diminishes in quantity 

 and fmally disappears. The main excurrent canals are surrounded 

 by a narrow layer of collenchymatous tissue in which the only 

 skeletal elements are scattered tylota and raphides. 



Spicules. — The megascleres, as already stated, are hardly distin- 

 guishable from those of T. digitata var. ruhicunda — even in size 

 being not materially different. The styli (when full-grown) vary 

 in length from 155 to 200/a, and are at most 6/x in diameter; the 

 tylota are never less than 175/zin length, and attain a maximum 

 size of 230 X 4 ^. The very slenderest immature tylota, it was 

 noticed, have the axial canal open at one end, and, at that end, 

 their spines are less advanced in development than at the other. 



Raphides (onychetse) occur of all lengths between 20 and 155/x, 

 but those exceeding 135 /x are scarce; there is also a rarity of indi- 

 viduals of certain intermediate sizes, with the consequence that, 

 roughly, three groups are recognisable, having the follow^ing 

 approximate ranges of length: (i.) 20-40 /* ; (ii.) 55-70 /x ; (iii.) 



