138 THE EUCRATEA. 



oiis curves, when its flat ribbon-like form was also 

 distinctly shown. It is evident, from the necessity of 

 the case, that this or any other retractor muscle must 

 perforate the integument and be inserted in the inner 

 surface, in order to sheath it in the manner in which 

 this operation is known to take place : but at what 

 point this perforation occurs, the transparency of the 

 parts forbids my detecting. 



There is a second muscle, (or rather perhaps a sym- 

 metrical pair,) inserted in the hinder wall of the cell 

 just below the point whence the new cell grows. Its 

 insertion here is broad, and it narrows upward ; I can 

 trace this to the bottom of the funnel of the gullet : 

 and its contraction is probably the first step in the 

 process of retractation. Beyond this point, the funnel 

 and the tentacles are not inverted, but descend directly 

 by the introversion of the integuments below them ; 

 the tentacles merely closing together in a fascia, as 

 they descend. 



Besides these, there are inserted within the horny 

 margin of the cell, some eight or ten bands, or perhaps 

 more, composed of parallel fibres. The course, and 

 use of these are very difficult to make out intelligibly, 

 from their apparently contradictory appearances in 

 different aspects and circumstances. I incline to 

 think however that they pass from the corneous rim, 

 to various parts of the lining membrane, and in 

 particular to that portion of it which covers-in the 

 broTtd aperture of the cell, — that which I have 

 described as prominently convex and protuberant 

 during the retractation of the animal, and concave 

 during its extrusion. I venture to presume that it is 



