146 Irving Hardesty 



tectorial membrane proper, and it is this matrix that maintains the 

 shape of the accessory membrane and holds the two sets of fibers, and 

 the fibers of each set, in their relative positions. 



The inner edge of this membrane consists of nothing but the crossing 

 inner ends of the fibers and is so exceedingly thin that it could not be 

 distinguished at all when lying in position but for the optical effect pro- 

 duced by the obliquely coursing set of fibers. The outer edge (the back 

 of the comb) is thicker than the inner, apparently resulting from a 

 gradual increase in the amount of the supporting matrix. In the outer 

 edge, the fibers of both sets seem to curl upward so as to produce a 

 short abrupt curl in this edge of the membrane with the convex side 

 toward the under surface of the tectorial membrane proper, as indi- 

 cated in the drawing of the end in Fig. 3. 



The question of the attachment of the accessory to the main 

 body of the tectorial membrane coiild not be definitely settled. The 

 accessory membrane was found so delicate that it would not stand 

 manipulation; in more deeply stained preparations it could not be 

 studied in its relations to the main body because of the light being 

 obscured in passing through the whole structure; transverse sections, 

 necessarily from dehydrated and embedded specimens, were entirely 

 impossible, and, in the unstained and lightly stained mounts, if attach- 

 ing fibers exist, they could not be distinguished in the maze of other 

 fibers present on both sides of their probable locality. From the study 

 made here, only this can be said : If the accessory membrane is attached 

 other than by light surface cohesion to the main body, it is most 

 probably attached along its outer, and thicker, edge. In several of my 

 mounts, the inner edge appeared folded over for short distances as 

 though it had been waving free in the fluids preliminary to the cover 

 glass, while the outer edge retained its normal position as though it 

 had behaved as a hinge. Further, the curled disposition of the fibers 

 in the outer edge suggest that their ends may be continuous into the 

 under surface of the tectorial membrane and that they may be broken, 

 ripped asunder, in cases in which portions of the accessory membrane 

 appear entirely free. 



As to its position, the accessory membrane lies under the outer zone 

 of the under surface of the tectorial membrane proper and to the outer 

 side of Hensen's stripe. It exists throughout the length of the tectorial 

 membrane. 



Like the tectorial membrane proper, it is widest at the apical enrl 

 and decreases in width toward the end of the basal coil. The decrease 



