E. IMPERIALIS. — YOUNG SPECIMENS. 79 



Young Specijiens. 



Of quite young E. inqyerialis, under 75 mm. length (excl. of 

 the basal tuft), I have been able to bring together no less than 

 a dozen specimens, of which the smallest (PI. II, fig. 6) measures 

 only 30 mm. in body-length and 10 mm. in greatest breadth. 

 They may be described in general as follows : 



The body is bellied in a spindle-like manner, straight or 

 slightly bent and circular in cross-section. Inferiorly it narrows 

 to a conically closed end, whence arise the basal spicules in a 

 small, almost solid tuft. Above, the body contracts in a much 

 less degree and ends almost truncated, the sieve-plate being only 

 slightly convex. The latter structure is very frail, the beams 

 being quite thin ; the angular meshes number from about half a 

 dozen to a score according to the size of the specimens. There 

 is yet scarcely a trace of the cuff. Numerous small parietal 

 oscula occur already in the smallest specimen above referred to. 

 The general form thus closely resembles that of young U. mar- 

 sJiall'i, in fact I think of all JS'tip/ec/e/Za species in the correspond- 

 ing stage of growth. 



However, there are certain points by which the similarly 

 sized young of E. impcrialis and E. marshalli may be distinguished. 

 Firstly, in the former the external surface presents a more jagged 

 appearance and shows a larger number of small, bristle-like, 

 prostal spicules, while in the hitter the broader and more con- 

 tinuous parietal ledges present on the whole a nearly even surface 

 {cfr. PL II, figs. 6 ct 7 with PI. IV, figs. 8 & 9). After attaining 

 a body-length of about 70 mm., the parietal ledges in E. imperialis 

 are already developed into the characteristic lappets or interrupted 



