No. I.] THE VERTEBRATE EAR. 5 1 



/. The basilar membrane. 



g. The cochlear nerves and nerve ends. 



h. Marsupials and Monotremes. 



The Cochlea. 



Alle physiologischen Individuen, gleichviel welche morphologische Individuali- 

 tats-Ordnung ihr materialles Substrat bildet, sind in alien ihren Leistungen und 

 Form-Verhaltnissen auf die morphologischen Individuen erster Ordnung, die Plas- 

 tiden (Cytoden oder Zellen) als " Elementar-Organismen " zuriickzufiihren, da jedes 

 Bion entweder selbst eine einfache Plastide (Monoplastis) oder ein Aggregat (Synu- 

 sie, Colenie, Complex) von mehreren Plastiden ist (Polyplastis). — Haeckel, Gen- 

 erelle Morphologic, I, p. 370. 



Der Organismus ist um so vollkommener, je abhangiger die gleichartigen Indivi- 

 dualitaten, welche ihn zusammensetzen, von einander und vom ganzen sind, und je 

 mehr also der ganze Organismus centralisirt ist, und alle subordinirten Individuali- 

 taten herrscht (Gesetz der Centralization). — Ibid. 372. 



Der Organismus ist um so vollkommener, je hoher zwischen alien untergeordneten 

 Individualitaten welche ihn zusammensetzen, der Grad der Arbeitstheilung und der 

 Grad der Wechselwirkung ist, je grosser mithin die Differenzirung und die Centrali- 

 zation des ganzen Organismus ist. — Ibid. 



The general features of the development of the organ of Corti 

 I have already given in the account of the morphology of the 

 sauropsid and mammalian cochlear organs. In the following 

 account which, though by no means exhaustive, will serve to 

 illustrate the ontogeny of the organ, I shall dwell almost entirely 

 on the organ of Corti proper, and shall have very little to say of 

 the other parts of the cochlear apparatus ; e.g. the scalse of the 

 cochlear walls except so far as they take part in the formation 

 of the organ of Corti, or influence the performance of its func- 

 tion. The account is mainly based on my studies of the devel- 

 opment as it occurs in the pig, although many facts have been 

 verified for the rabbit, sheep, ox, opossum, and other mammals. 



So far as my observations go, and they agree with Boettcher's, 

 there are but the slightest differences noticeable in the develop- 

 ment of the ear among the domestic mammals, the only ones 

 heretofore studied with a sufficient degree of completeness for 

 the purpose of comparison. 



The first thing of fundamental importance to be noted is that 

 the cochlear tube is accompanied on its sense-organ wall or floor 

 by a ganglionic nerve trunk {11. cochlccE), an artery {a. basilaris 

 cochlecB) of which the vascula spiralis is one branch, a vein (z/. 

 basilaris cochlccB), and a lymphatic canal of large proportions ; 



