1 86 AYERS. [Vol. VI. 



account of the development in Tropidonotus natrix, to which he 

 has added much in the way of detail. 



After a very short account of the early transformation pro- 

 cesses in Lacerta, in which Hoffmann merely confirms the prev- 

 alent ideas of the origin, mode of growth, and early relations 

 of the auditory vesicle, he passes on to a more detailed account 

 of the later transformations of the growing ear. He states 

 (p. 2012) that the auditory vesicle rests on the large auditory 

 facial ganglion as on a cushion, the inner face being covered by 

 the ganglionic mass, which also reaches around onto the ante- 

 rior, posterior, and ventral faces of the vesicle. 



The auditory flask has been so displaced with reference to its 

 original position that its originally relatively large opening, now 

 very much reduced and on the verge of closure, appears as 

 though pushed dorsad. After the closure of the external pore 

 of the endolymphatic duct it remains for a time connected with 

 the epidermis. The separation is finally completed, but only 

 after the canals have begun to form, and the whole structure 

 has been pushed ventrad to near its final position at the side of 

 the medulla. 



The closed endolymphatic duct reaches dorsad by a much 

 narrowed portion quite to the ectoderm. This process is the 

 recessus labyrinthi or aquaeductus vestibuli of the authors. 



Hoffmann observes that " Es scheint mir denn auch wohl 

 nicht zweifelhaft, dass dieser Anhang oder dieser stielformige 

 Fortsatz dem langen, diinnen Rohr entspricht, welches bei 

 den Selachiern das knorpelige Primordialcranium durchbohrt, 

 dorsalwarts mit der Epidermis der Korperoberflache in verbin- 

 dung steht und dort eine offene Ausmiindung besitzt, wo dem 

 zufolge eine Verbindung des zum Labyrinth sich umwandelden 

 Hohrblaschens mit der Korperoberflache dauernd fortbestehen 

 bleibt," a conclusion justified by the facts of development and 

 adult structure, not alone for the Reptilia, but as well for all other 

 vertebrates in which the primitive endolymphatic duct closes 

 early in development or appears only relatively late in ontogeny 

 as an outgrowth of the utriculo-sacculus. In the latter case it is 

 an atavistic phenomenon, and is an excellent illustration of the 

 great degree of persistency of structures which, although no 

 longer possessing important functions, at the same time do not 

 in any way prevent the functional perfection of the organ or 



