104 I. IJOIA : HEXACTINELLIDA, I. 



In all the young siieciraens the tubular body has in general 

 a spuidle-like ventricose shape (PI. IV, figs. 6-9). At first the 

 ventricosity is situated at about the middle of the body ; it may 

 however soon be brought to a somewhat lower level, probably 

 because the growth in length at the upper end is relatively more 

 rapid than the general increase in circumference. The lower end 

 is contracted and blindly closed at its juncture with the yet 

 weakly developed basal tuft. The upper end is truncated unless 

 the more or less convexly arched sievs-plate, which is very 

 delicate and therefore easily detached in the early stage of its 

 formation, is preserved iutact. 



The smallest specimen I have had was only 18 mm. long 

 (exclusive of the basal tuft), 7 mm. broad at the middle and 

 2 mm. wide across the round opening at the superior end. Three 

 other very small specimens measured 20-23 mm. in length, 7-9 

 mm. in greatest breadth and 272-4 mm. across the superior 

 truncated end. One of these specimens is shown in natural size 

 on PL IV, fig. 6. The entire external surface is on the whole 

 even and covered over uninterruptedly by the dermal layer. A 

 few isolated gaps seen in the superficial tissue proved on close 

 observation to be rents due to laceration. Unless the wall has 

 become untransparent by drying up, the longitudinal beams of 

 the skeleton can be made out to a greater or less extent, while 

 the transverse beams are quite indistinct. The canals in the 

 wall appear to the naked eye as darkish spots, which become 

 smaller toward either end of the body and finally are hardly 

 visible, so that the wall tissue at the ends assumes a uniformly 

 whitish appearance. Of the delicate sieve-plate, which must have 

 been present at the open upper end but which seems to have 

 been lost, I shall speak further on. 



