No. I.] THE VERTEBRATE EAR. 233 



they issue from the brain. At the point of junction the two 

 half-pores united into a single pore, which in some fish forms 

 {e.g. Torpedo) persists as the outer opening of the endolym- 

 phatic duct, and the only persisting indications of the separate 

 origin of these organs and their canals is their nerve supply. 

 It is a necessary consequence of the great functional differen- 

 tiation which the ear organs have suffered that their nerves 

 should also become much increased in size, and instead of ap- 

 pearing now as nerve branches they have become really larger 

 than the parent nerves from which they arose. (Cuts i and 25, 

 PI. I, Figs. I, 15, and 16, and PL IX, Figs. 2, 3, and 4.) 



The vertebrate and invertebrate auditory organs, although 

 parallel and analogous developments, are in no sense homolo- 

 gous structures, notwithstanding the apparent homology of the 

 embryonic organs at one stage of their development in verte- 

 brates with those of the invertebrates. 



The only attempt to utilize the facts of embryology to obtain 

 a solution of the phylogenetic questions of the vertebrate semi- 

 circular canals is that made by von Noorden, and illustrates 

 how completely he failed to comprehend the significance of the 

 transformation processes within the ear of the bony fish, which 

 he had so clearly seen and described. Our author gives a 

 purely teleological explanation of the processes he studied, and 

 makes no attempt to bring them into harmony with the proc- 

 esses of canal development, of which he was cognizant in other 

 forms — mammals especially. In conclusion, von Noorden 

 expressed a conviction that the study in other forms of the 

 processes he had described for bony fishes would, to use his 

 words, "manches neu und interresante zu Tage bringen." 



I quote his explanation mainly because it is unique in the 

 literature of the subject, and because it serves to show how far 

 away from a comprehension of the significance of the details of 

 auditory development even the investigators in this field have 

 been. 



"Der Weg, den die Natur einschlagt, um zum Ziele zu 

 gelangen, ist ein ausserordentlich einfacher. Das Problem, 

 welches sie zu losen hatte, war : aus einer einfachen Hohlkugel 

 einen Raum mit mehreren Abtheilungen herzustellen. Die 

 Natur umgeht es, die einmal angelegte Wand, welche den 

 Hohlraum von der Umgebung scheidet, in ihrer Form zu 



