Kingsbury, Brain of Nectunis, 195 



precommissure of higher forms. Numbers of myelinic fibers 

 from the basal prosencephalic tracts decussate in it and also 

 dorsad to it. Immediately above it is the callosum of Osborn, 

 here called for distinction 'dorsal commissure.' 



Basal Prosencephalic Tract. — As has been stated by Fish 

 ('95), the fiber bundle thus designated has received various 

 names. Of these the term applied by Edinger, * Basale Vor- 

 derhirnbiindel ' seems to the writer most appropriate and the 

 English equivalent employed by Osborn, ' basal prosencephalic 

 tract' {b. p. t. of the figures) is used. The term "peduncle" 

 employed by Herrick and Fish is misleading since these tracts 

 are not the equivalent of the pediinculi cerebri, or crura. Were 

 there no false homology implied, the term peduncle would still 

 be objectionable because of the possible confusion with the 

 peduncles of the cerebellum. 



Edinger ('93, p. 31) speaks as follows of this tract: "Das 

 Vorderhirn der Knochenfische besitzt an der Basis ein macht- 



iges Stammganglion, Corpus Striatum, Das Stamm- 



ganglion andert nun von den Fischen bis hinauf zum Menschen 

 seine Lage und sein relatives Grossenverhaltniss nicht mehr 

 wesentlich. Am gleichen Orte finden wir uberall die gleichge- 

 baute Anhaufung von Ganglionzellen, uberall entspringt aus ihr 

 ein machtiges Faserbiindel, das sich caudalwarts wendet und 

 immer in Ganglien des Zwischen- und Mittelhirn sich auflost. Es 

 heisst basales Vorderhirnbiindel und ist fiir Sanger seit Langem 

 als Linsenkernfaserung bekannt. " On pages 93 and 94 is given 

 a further discussion of the representative of this bundle in the 

 mammalian brain. 



In Nectunis these tracts may be recognized first in the 

 caudal portion of the diencephal where the fibers which form 

 them are rather diffuse. Farther cephalad it is augmented by 

 several bundles of amyelinic fibers which come from the thala- 

 mus ( Fig. 23) and at the level of the optic nerve it has become 

 a well marked round bundle ( Fig. 28) containing both myelinic 

 and amyelinic fibers. Apparently few fibers come from the 

 mesencephal, none farther caudad ; a small portion also seems 

 to come from the infundibular region. It passes into the latere- 



