No. I.] THE VERTEBRATE EAR. 20I 



standigkeit zu besitzen scheint imd durch die Eigenthiimlichkeit 

 ihres Baues das Interesse in hohem Grade in Anspruch nimmt. 

 Sie ist jedoch kein einheitliches Gebilde, insofern an ihrer 

 Zusammensetzimg ganz verscheidene Formelemente Antheil 

 haben." 



Boettcher never saw Deiters's transverse nerve fibres in the 

 cochlea, which are equivalent to Kolliker's longitudinal system 

 of cochlear nerves. He thus criticises the view (p. 169) : 

 " Abgesehen davon ist ihr Vorkommen zwischen den Bogen- 

 fasern, wie schon E. Rosenberg, angegeben hat, mit der Ent- 

 wicklung dieser nicht gut vereinbar und was die longitudinalen 

 Ziige betrifft, welche weiter nach aussen zwischen den ausseren 

 absteigenden Horzellen verlaufen sollen, so ist auch deren Exis- 

 tenz aus theoretischen Griinden zu bestreiten, well der Raum 

 zwischen ihnen von den aufsteigenden Zellen ganz ausgef iillt ist." 



Pritchard (1878, 217) gives the following account of the devel- 

 opment of the organ of Corti. Outside of the group of long 

 cells which fill the sulcus spiralis in the embryo there lie five 

 somewhat shorter cells (his primary cells), of which No. i 

 (counting from in, outwards) divides itself transversely into 2. 

 Nos. 3, 4, 5 acquire two nuclei each by the division of the par- 

 ent nucleus. The outer four (2, 3, 4, 5) form the four hair cells 

 of the outer rows from their upper parts, and the Deiters cells 

 of their lower parts. From each Corti's cell shoots up a process 

 which later splits into the hairs. Cell No. 2 becomes more 

 triangular (in perpendicular section of the organ) by the broad- 

 ening of its base. Its nucleus grows and divides between 

 the two ; a vacuole appears in the common protoplasm — the 

 rudimentary tunnel. The lateral walls of the cell {i.e. inner 

 and outer walls) have developed into the rods of Corti. The 

 membrana reticularis originates out of the union of the upper 

 ends of the primitive cylindrical epithelial cells. In the same 

 way that the walls of these cells develop into the trabeculse or 

 perpendicular fibres which stretch from the membrana reticu- 

 laris, to the membrana basilaris, and are homologous with the 

 Miillerian fibres of the retina. Pritchard concludes that Corti's 

 arches, the trabeculse, the membrana reticularis, develop out of 

 the walls of the primitive epithelium, the hair cells out of the 

 cell contents, while the membrana tectoria is a secretion from 

 them. The views here expressed show that this author did not 



