J28 "ENDEAVOUR" SCIENTIFIC RESULTS. 



of the latter, that they prmecd frum the apex of the conulus, 

 and after running inwards, with gradually increasing di\er- 

 gence, for a short distance towards the sponge-interior, 

 gradually curve round and return again to meet the surface 

 at varying distances from their starting point- the more cen- 

 trally situated fibres of the pencil proceeding to a further 

 distance than the more peripheral. Styli similar to those com- 

 posing the fibres are sparingly scattered through the tissues 

 together with discasters of two kinds, a larger and a smaller. 

 The former are closely aggregated in the immediate surround- 

 ing of all the main fibres encircling them as a kind of loose 

 sheath. The cortical skeleton is a layer of closely packed 

 discasters almost exclusivel\- t)f the larger kind ; it is about 

 300 to 400 ^i in thickness. 



Megascleres. — These are styli, probably of a single kind — 

 the stouter with a more or less blunt or rounded distal ex- 

 tremity, and occasionally becoming almost perfectly stron- 

 gylote ; the slenderest usually sharply pointed. They are 

 sometimes elongately subtylote at the basal end, and ha\e a 

 maximum size of 365 x 1 i |<. 



Microsderes. — (i.) The larger discasters are stout spicules, 

 having a short central region devoid of spines, and on 

 either side of this two more or less distinct whorls of 

 large spines : those of the terminal whorl projecting 

 obliquely forwards; those of the sub-terminal, stand- 

 ing more or less perpendicularly to the spicule-axis. 

 They are about 40 ]i in length (exclusive of spines), 

 and have a diameter in their spineless central region 

 of about \2 ;(. The spines are 10 to 12 ]i long, 

 (ii.) The smaller discasters are very variable in form, no 

 two apparently being quite alike. They are much 

 slenderer spicules than the preceding, with an elon- 

 gated spineless central region, and at either end, two 

 more or less distinct whorls of simple or (more usually) 

 compound spines, the latter of which are columnar in 

 form, with a few terminal spinules. The terminal 

 whorl of spines is often reduced and then appears as 

 a prolongation of the axis of the spicule. These 

 spicules are at most 38 ]i in length (inclusive of 

 spines), and have a diameter centrally of i to 4 ji 

 (rarely more than J. 5 ]i). The stouter individuals 

 may represent a third kind of discaster intermediate 

 between the other two. 



Loc. — North coast of Tasmania, off Devonport. ("En- 

 deavour.") 



