60 



The other specimen, the soft parts of which are not so well preserved, is 

 11 cm. long, has a maximum breadth of 3 cm. and is on the whole similar to the 

 one described above. In consequence of its greater age the parietal apertures are 

 farther apart and also a little larger. The root-tuft is over 2 cm. long and 

 comparatively well preserved. Its lower end is anchored to a mass of thin and 

 long worm-tubes (pi. XI, f, 1). 



Most of the principalia-spicules of the skeleton-net supporting the tube- 

 wall are stout oxystauractines and oxyhexactines. The longitudinal rays of these 

 spicules lie nearer to the outer, the transverse rays nearer to the inner surface of 

 the tube- wall. The former are 1-3 mm. long, the latter shorter. In the longitu- 

 dinal and transverse fibres composing the skeleton-net, hexactines and staurac- 

 tines alternate regularly, so that every second crossing-point of the fibres is 

 formed by the centre of one of the former and every other by the centre of 

 one of the latter. The radial, distal rays of the stout principal hexactines form 

 the spines above described, which protrude from the outer surface. They are 

 5 mm. long, smooth at the base, and spined in the distal, freely projecting part. 

 Below, the spines are quite short, further on they become higher, but towards 

 the distal end they are again reduced in length. The proximal radial ray, lying 

 opposite to the distal one, is comparatively small and appears rudimentary. It 

 is 500 h long, smooth, and rapidly attenuated to a blunt, sometimes slightly inflat- 

 ed end >pl. XI, f. 5,7). 



Thin comitalia accompany the principalia of the tube-wall in not very great 

 numbers. They are mostly triactines, with two long rays extending in a straight 

 line and a third, much shorter one, vertical to the other two. Also diactine, 

 stauractine, pentactine and hexactine comitalia are met with. The rays of the 

 comitalia end nearly always with a slight tuberculous, club-shaped terminal in- 

 flation. The numerous oxydiactines attached to the distal protruding rays of the 

 hexactine principalia are also to be considered as comitalia. They are about 

 500 /^ long, slightly rough and have in the middle an elongated, spindle-shaped, 

 not sharply defined thickening. These spicules are slightly spirally twisted and 

 firmly cling to the spined, distal parts of the projecting radial rays of the hexac- 

 tine principaha, which they entwine (pi. XI, f. 4, 5). 



The root-tufts of the older specimen is 2-3 cm. long. They are composed 

 of the same well-known two kinds of anchor-spicules which are met with in 

 EiqAectella aspergillam and EwplecteJla simplex and which have been described 

 above in the latter. It is probable that the root-tuft is in all Euplectella-species 

 composed of such spicules. 



The stout, sword-shaped, hexactine supporting-spicules of the dermal 

 membrane, the hypodermalia, and the more slender pentactine supporting-spicules 

 of the gastral membrane, the bypogastralia, do not essentially differ in shape. 



