138 IrA'ing Hardesty 



surface of the phalauges is widest at the apex of the cochlea and grows 

 narrower towards the base of the coil, just as the rods and the angle 

 they form decrease in size, and it was found that the stripe is somewhat 

 wider at the apex and decreases in width toward the base, but at no 

 level was it found to be as wide as the groove floored by the phalanges, 

 nor does it vary in width as much as the groove. The only inference 

 drawn from this study is that Hensen's stripe probably has the form 

 of a low ridge the existence of which may be protected by the groove 

 over which it lies. 



In looking over papers dealing with the development of the tec- 

 torial membrane and the sections from pig foetuses prepared here for 

 the purpose, the possibility was suggested that Hensen's stripe may 

 have an embryonic significance: namely, that it represent? that area 

 or line on the under surface which is last to become detached from the 

 cells which give origin to the membrane. 



On the Development of the Membrane. 



It is not the object of this paper to describe in detail the development 

 of the tectorial membrane. All the essential stages of the process have 

 already been worked out quite thoroughly. Kolliker, '61, Middendorf, 

 Eosenberg, Gottstein, Nuel, Eetzius, Schwalbe, Bottcher, Hensen, 

 Prichard, Exner and Eickenbacher, '01, all agree that, in vertebrates, 

 the membrane is a cuticular structure arising from the thickened epi- 

 thelium of the inner side of the floor of the embryonic cochlear canal, 

 and Kuhn and Hasse have described a similar origin for invertebrates. 

 I find that in pigs of 2.5 cm. there has begun the marked thickening of 

 the epithelium of that side of the cochlear canal which will become the 

 portion to line the spiral sulcus and overlie the inner portion of the 

 basilar membrane. At 3 cm. the thickening of the epithelium has 

 increased and there appears above the entire thickening a cuticular film 

 of quite appreciable thickness and decided fibrous character. The later 

 stages, up to about 12 em., show increase in the width of the epithelial 

 thickening corresponding to the increase in the diameter of the cochlear 

 canal, consequent increase in the width of the developing tectorial 

 membrane and marked increase in the thickness of the epithelium con- 

 cerned. At 12 cm., or shortly before, there is differentiated a second 

 and much smaller epithelial thickening along the immediate outer edge 

 of the first one, thus giving the greater and the lesser epithelial thicken- 



