63 



The tough basal root-tuft, which arises from the longitudinal spicular fibres 

 of the lower, attenuated, funnel-shaped end of the sponge-tube and forms further 

 down a compact bundle of fibres in no way differs from the root-tufts of other 

 Euplectella-species, Eupledella aspergillum for instance. 



The whole of the tubular sponge is soft and, particularly in its upper and 

 middle portion, so lax that it collapses on being removed from the liquid in which 

 it is preserved. The lower, funnel-shaped, terminal part is harder. 



The spicular fibres of the main supporting skeleton are 333-500 /"■ thick, 

 arranged longitudinally and transversely and cross each other at right angles. 

 These fibres are chiefly composed of stout stauractines with rays up to 200 h- thick. 

 The longitudinal rays of these spicules are nearly straight and attain a length of 

 several centimeters; in the lower part of the body they are as much as 5 cm. long. 

 The transverse rays are curved in accordance with the curvature of the tube- 

 wall in which they lie, and are rarely more than 3 cm. long. The transverse 

 rays lie close to the inner surface of the tube- wall, the longitudinal rays are nearer 

 to the outer surface : they lie on the transverse ones like rails on sleepers. To 

 attain such a position outside the ideal cylinder-surface in which they would 

 otherwise lie, the rays, particularly the transverse ones, are abruptly curved. 

 A short distance from the centre of the spicule these rays are bent inwards to- 

 wards the axis of the sponge, and then again outward, whilst the. longitudinal 

 rays often nearly retain their ordinary position in a straight line. I never found 

 in these spicules a fifth distal ray ; they are always strictly tetractine and never 

 pentactine as the principalia of some other Buplectella species. 



These principal stauractines are accompanied by varying numbers of much 

 thinner, smooth and long triactine and diactine, closely attached comitalia. The 

 rays of the latter terminate with slight club-shaped thickenings pointed at the 

 end, and rough or covered with short spines. The triactine comitalia consist of 

 two long opposite rays lying in a straight line and a third, much shorter ray, 

 vertical to the other two and usually slightly curved. 



The transverse and longitudinal spicular fibres are similar in composition, 

 both consisting of the rays of the stout stauractine principalia and the slender 

 comitalia described above. The intervals between the circular, hoop-like, trans- 

 verse fibres are narrowest near the upper end of the sponge ; downwards, towards 

 the lower end of the body, they uniformly increase in breadth. The longitudinal 

 fibres are furthest apart in the central, inflated part ; upwards and downwards, 

 towards the ends of the body, they approach each other. The rectangular meshes 

 formed by these fibres are accordingly nearly quadratic in the upper and central 

 part of the body, whilst they become considerably elongated towards the lower 

 end. Where the longitudinal fibres have recently multiplied by fission and conse- 

 quently lie nearer together, such elongated meshes are also seen in the central 

 part of the body. 



