608 THE SENSES AND SENSORY ORGANS. 
mounted entire as a microscopical object, its form is more 
complicated. Lee was, I believe, the first who accurately 
described the form it assumes, but he regarded it as its natural 
condition. 
The integument of the capitellum is soft, except in three 
lines, two of which are prolongations of the anterior, and one 
of the posterior, portion of the scape. When the capitellum 
is shrivelled or compressed, these portions of the integument 
become salient, and the proximal portion of the capitellum 
becomes subpyramidal with three triangular faces. _ The distal 
portion is then seen to be deeply grooved, so that it is divided 
into a proximal and distal portion. This groove is not visible 
in the fresh halter, but is very apparent in most preparations. 
It forms a spiral and is the line of attachment for the septum. 
The groove commences on the inferior surface, close to three or 
four large bristles, and terminates at a point nearly in the 
same line, but at a more distal part of the capitellum. It is 
deepest at its commencement. 
A curved sheet of elongated cells extends from this groove 
to the septum of the scape, and forms the septum of the 
capitellum. One of the canals of the scape terminates on 
either side of this septum; and the two cavities into which it 
divides the capitellum communicate at the free edge of the 
septum, so that a current of fluid passing from one canal to 
the other takes a spiral course in the capitellum. 
It is not easy to describe the exact course of the septum in 
the capitellum, but it may be compared to a single turn of the 
spiral septum of a cochlea. Its edges are seen in a com- 
pressed halter as a figure of 8. Its proximal portion is 
attached on either side to one of the ridges on the capitellum 
proceeding from the anterior canal of the scape. It is sub- 
triangular, and its plane is axial to the scape and capitellum ; 
its distal part curves into a plane approximately transverse to 
the axis of the scape, and is inserted into the spiral line 
already described ; it presents a free edge where it terminates 
in the vicinity of the three or four long sete, where the spiral 
groove formed by its insertion is deepest. The relations of the 
