228 "ENDEAVOUE" SCIENTIFIC EESULTS. 



There are apparently no oscula. The consistency in alcohol 

 is firm and fairly tough ; specimens which have been dried 

 after initial preservation in alcohol are rather brittle for a 

 species of Clathria. 



The skeleton is a fairly regular sub-rectangular reticulation 

 consisting of (i.) semi-plumose main fibres which run longi- 

 tudinally with gradually increasing trend outwards from the 

 axis of the branch to the surface, where they terminate in a 

 tuft of spongin-free spicules; and (ii.) simple connecting fibres 

 of a spicule's length which cross these at right angles and con- 

 tain, each of them, one or (less frequently) several axial 

 spicules. The pattern of the skeleton might therefore be des- 

 cribed as scalariform. On the whole, the fibres are not rich in 

 spongin, and the chief part in the composition of the skeleton 

 is played by the spicules. The directive spicules of the main 

 fibres, /.t'., the principal styli, which are very loosely associated 

 and generally number less than five in a cross-section of the 

 fibre, are for the most part disposed obliquely with regard to 

 the axis of the fibre ; and consequently their distal or pointed 

 extremities frequently project beyond the spongin. Towards 

 the outer extremity of the fibres, the obliquity of the spicules 

 increases and the amount of spongin in the fibre diminishes ; 

 in this portion of their length the fibres present an appearance 

 which recalls that which is characteristic of the C. spicata 

 group of species {vide p. 214). Accessory styli are rather 

 plentiful, and occur only as echinating spicules. Auxiliary 

 tylostyli are scattered between the fibres, increasing in num- 

 bers in the vicinity of the surface ; their mode of arrangement 

 in the dermal layer is similar to that described for C. arcuo- 

 phova. Principal styli also occur interstitially in noteworthy 

 number; these lie in close proximity to, and parallel with, the 

 fibres, and frequently point in the direction opposite to that of 

 the spicules within the fibres. 



Megasclercs. — 



(i.) The principal styli are curved sub-conical smooth 

 spicules which not only vary greatly in maximum size 

 in the different forms of the species, but also exhibit 

 a considerable range in size in any given specimen. 

 The smallest are never much larger than the longest 

 accessory spicules, and in one of the forms of the 

 species there appears to be an unbroken continuity 

 in regard both to size and form between the megas- 

 clere's of the two kinds. The largest spicules are 

 invariablv to be found amongst those which form the 

 surface-tufts; but their maximum size, owing to the 

 relative fewness of the spicules which approach it, is 



