No. I.] THE VERTEBRATE EAR. 21/ 



Kupffer's objection that, in the case of the V and X ganglia, 

 he was unable to detect anything like a sensory epithelium is 

 hardly valid ; for, in the case of the auditory vesicle, a relatively 

 long period elapses after it is invaginated before it forms the 

 isolated sensory epithelial patches ; and considering that the 

 V and X (auct.) do supply the sense organs of the lateral line 

 throughout their territory, we cannot hesitate to accept such 

 important testimony for its full value. Kupffer calls attention 

 to the fact that these structures have the following things in 

 common. First, they arise from a common Anlage. Second, 

 they arise in the same horizon in the dorsal region of the body. 

 Third, they have fundamentally the same mode of formation. 

 Fourth, they have the same relations to the dorsal roots of their 

 respective nerves. 



Relative to the kinship between Cyclostomes and Gnatho- 

 stomes, I quote Gegenbaur's opinion as expressed in a notice of 

 Retzius's work (98, 1885) p. 127: — 



"Von grossem Interesse ist es, zu sehen, wie die jeweilige 

 Organisationsstufe des Labyrinthes im Wesentlichen mit der 

 iibrigen Organisation harmonirt, indem sie innerhalb einer ge- 

 wissen Grenze sich halt. Unsere Vorstellungen von der Phylo- 

 genie der Wirbelthiere finden damit eine neue Bestatigung. 

 So stellen sich die Cyclostomen von den iibrigen Vertebraten, 

 den Gnathostomen — so weit entfernt dass nicht einmal deren 

 Bogengange eine strenge Vergleichung mit denen des letzteren 

 zulassen. Dieses bestatigt nur die grosse Bedenklichkeit der 

 Schliisse, die von der Organisation der Cyclostomen auf jene 

 der Gnathostomen ohne Weiteres gezogen zu werden pflegen." 

 It is not the least service which the anatomical facts brought 

 together here have rendered, that they have proved that so far 

 as the ear is concerned there is a direct relation between these 

 two groups of animals, and that the former stand as the ances- 

 tors of the Gnathostomes. Whence, instead of rendering the 

 phylogeny of the Gnathostomes more difficult, and isolating 

 the Cyclostomes into unknown relations, the facts of auditory 

 anatomy so far as yet worked out indicate the contrary in 

 a very instructive manner. As we now know their auditory 

 anatomy, the differences between Myxine and Petromyzon are 

 in many respects as great as between Petromyzon and the 

 fishes, and yet the two former undoubtedly belong to the same 



