= 
287 
weil uns der Beweis unserer aprioristischen Vermutung fiir Hirnfelder 
gelungen ist, in bezug auf welche die bisher allgemein herrschenden 
Anschauungen durchaus das Gegenteil lehrten. 
Wir sind ferner — wie ich in Rostock betont habe — auf Grund 
unserer Erfahrungen dazu gekommen, auch noch die myeloarchitek- 
tonische Rindenfelderung gegenüber der cytoarchitektonischen in den 
Hintergrund treten zu lassen. Damit verliert die myelogenetische 
natürlich noch mehr an Bedeutung. 
Nachdruck verboten. 
The fifth and sixth Aortie Arches in Chick Embryos 
with Comments on the Condition of the same Vessels in other 
Vertebrates. 
By Wıruıam A. Locy, 
Director of the Zoölogical Laboratory of Northwestern University, 
Evanston, Illinois, U.S.A. 
With 10 Figs. 
The main features of the development of the aortic arches in 
vertebrates have long been known, nevertheless, the extraordinary 
changes which they undergo in a relatively short space of time, makes 
it difficult to decide upon some points of primary interest to anatomists. 
Among the matters still called in question is that of the homology 
throughout the series of air-breathing vertebrates of the arch from 
which the pulmonary artery springs. The solution of this question 
depends mainly upon whether there are five or six aortic arches in 
the embryonic stages of birds and mammals. 
von Baur, who in 1827 and ’28 first gave an account of the 
development and transformation of the aortic arches in birds and mam- 
mals, was not troubled by questions of this nature. Neither was 
RatHKE, whose work (1843, 1857) embraced a particular examination 
of reptiles, birds and mammals, but who did not happen upon evidence 
to indicate a larger number than five aortic arches in any of the forms 
studied. 
In 1886, however, Van BEuMELEN pointed out the presence in 
reptilian embryos and the chick, of a rudimentary arch between the 
systemic and pulmonic arches, and, since that time the question of the 
number in higher vertebrates has been a present one in comparative 
anatomy. 
The discovery of Van BEMMELEN was of great interest in connec- 
tion with the previous observations of Boas (’81, ’82, ’86) to the effect 
