i82 Recent Literature. [zoe 



A systematic classification giving the distinctive features of each 

 class and order follows, the account closing with a i^^ general re- 

 marks on the life and history of the group in question. Although 

 dealing primarily with anatomy, the external form, habits and gen- 

 eral classification of animals are by no means slighted. c.a.k. 



Jom-nal of Morphology, W, 1-360. Vertebrate Cephalogenesis. 

 II. A Contribution to the Morphology of the Vertebrate Ear, with 

 a Reconsideration of its Functions. By Howard Ayers. In this 

 work a lengthy and exceedingly important investigation of the em- 

 bryology, morphology and physiology of the cordate ear is pre- 

 sented. The author has made an exhaustive examination of a great 

 number of representative types, and. as a result, revolutionizes many 

 of the generally accepted ideas, both of the development structure 

 and functions of many of the parts of the ear. The work is illus- 

 trated with twelve plates and a number of diagrams and figures. 

 Mr. Ayers concludes from his investigations that the vertebrate ear 

 is not related phylogenetically to the invertebrate, but is formed by 

 the union of two sense organs — the superficial canal complex. He 

 finds a close connection between the ear of the alligator and of 

 mammals, and considers that the organ of Corti of the latter is a 

 direct descendent of the organ of Corti in the former. This modi- 

 fies the position of birds in the scale, so far as the morphology of 

 the ear is concerned. The author says: " Having found, from m}^ 

 own investigations, in three groups of birds — Rasores (Gallus), 

 Columbinse (Columba), and Passeres (Mimus) — that the develop- 

 ment of the cochlea is not so far advanced as in the hydrosaurian 

 reptilia, it will be necessary to change the view advocated by Hasse, 

 according to which the saurian reptilia stand as transitional forms 

 between the amphibia and the lower reptilia and the birds, for it is 

 obvious that in cochlear anatomy the birds hold a place apart from 

 the direct line of descent as typified in the mammalian cochlea." * 



Mr. Ayers' generalizations with regard to the development of the 

 ear are of great importance. "Although oyitogenetic evidence." he 

 says, t " seems to lead to the conclusion that the auditory organ 

 arose by the invagination of a single superficial sense organ, it is by 

 no means certain that this is true, for there are certain facts of com- 

 parative anatomy and certain phylogenetic considerations which 



* P. 227. t P. 231. 



