Ixxx 



INTRODUCTION. 



pended in a kind of cleft at its upper extremity, in which 

 it works backwards and forwards. The seta (or bristle) 



Fig. xli. 



-P 



Vibraculum of ScruiDocellaria scruposa. 



VC. Vibracular chamber, m. Muscles, pp. Pointed extremities of the 



chamber, between which the seta is suspended. S. Seta. 



is broad at the base, and above it slender, and often of 

 considerable length. In some cases it attains an enor- 

 mous development, and forms either a whip-like appen- 

 dage or an organ of such a size and strength as to be 

 available for locomotive purposes. On the lower part of 

 the wall of the chamber there is always a small opening, 

 marking the point from which a long tubular appendage 

 (or radical fibre) oi'iginates (Plate VI. fig. 8, and Plate 

 VII. fig. 2). 



The vibraculum, as already mentioned, is of compara- 



