ECHINUS. 131 



object may not mislead the obsem-er, would require investigation. Under 

 one view, the hair is croAviied by a globular formation, of solid appear- 

 ance. Under the other, the summit is partitioned into three divisions 

 or members, resembhng leaves opening and closing, Idie so many forceps, 

 to clasp and retain minute fragments between them. From this summit, 

 being trifid in one species, it is denoniinated Pedicellaria tridens by 

 MUUer. The hair or stalk seems cylindrical, and sometimes as if oc- 

 cupied by a channel or internal substance in a vacuity. 



The length of the longest stalk is about ten or twelve times the 

 diameter of the expanding leaves. Here, these leaves or arms of the 

 forceps, are variously shaped, as maj'' be seen on inspecting the figures ; 

 and they are often very active. 



From the examination of many, this portion is found of different 

 conformation in various specimens. Thus : — 



1. The head is very short, as if imperfectly developed. 



2. The head, when closed, is large, and resembles a minute pomegran- 

 ate ; but when opening completely, the ai-ms of the forceps of some speci- 

 mens seem to terminate in a long claw. 



3. The head resembles that of a duck. It is verj- long when closed, 

 ■with three arms like the maudililes of that animal, which are apparently 

 serrate. When emploj^ed actively, all the arms unfold with singular 

 motion, and stand almost at right angles to the stalk. 



Pedicellaria3 cover the Echinus in thousands. They are of various 

 dimensions in large specimens, some half an inch long. If rising from 

 the fine red epidermis when present, their motion is well exposed, as re- 

 sembling the inflection of the suckers, — bending from side to side, the 

 head describing nearly a cu'cle by the turning of the stalk, — the whole in 

 great activity. But there is no essential difference between the figure and 

 the motion of the Pedicellariae on the larger and on the smaller Echini. 

 The stem is certainly hollow, and it may be that the lower part affixed 

 to the epidermis or to the shell is rigid. The Pedicellariae are dispersed 

 everywhei^e among the spines, also on the bare portion which surrounds 

 the mouth of the living animal. They are not alike numerous in all 

 specimens.— Plate XXXII. figs. 6, 7, 8, 9 10, 11. 



