AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, OCTOBER 2 
POINTS OF VIEW CONCERNING FOREBRAIN 
MORPHOLOGY IN LOWER VERTEBRATES 
NILS HOLMGREN 
University of Stockholm 
FORTY-TWO FIGURES (NINE PLATES) 
For some years I have been occupied with investigations upon 
the brain structure of different vertebrates. I have paid much 
attention to the morphology of the forebrain, which seems to 
me not sufficiently understood by former workers. I have thus 
made extensive studies on this part of the brain in Myxine and 
bony fishes. In addition, I have made studies on Petromyzon, 
selachians, holocephalians, ganoids, amphibians, reptiles, and 
mammals, studies which, however, have not yet resulted in 
publications, but have nevertheless given many valuable points 
of view concerning forebrain morphology, some of which are 
subjects of special investigations at this institute and under my 
direction. 
In vertebrates there are two different types of forebrain present, 
the everted and the inverted. The everted is confined to Polyp- 
terus, ganoids, and teleosts, the inverted to all other vertebrates. 
The essential difference between these two types is, that in the 
former the dorsal walls of the forebrain are bent outward, while 
in the latter they are bent inward so as to form the roof of the 
brain. In the everted forebrain the roof is made up by the 
greatly expanded tela. 
Concerning the inverted type, it may be accentuated that the 
process of inversion, that takes place in a very early embryonic 
stage and is very soon followed by an evagination process, results 
in the formation of the hemispheres. This evagination process 
not only widens the brain cavity in the lateral direction, but also 
evaginates the lateral ventricles forward and backward to form 
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