( 695 ) 
Physiology. — ‘On the infundibular region of the brain of 
Amphiorus lanceolatus”, By Dr. J. Boeke. (Communicated by 
Prof. T. PLACE). 
In connection with the hypothesis that the part of the saccus 
vasculosus in Ichthyopsida described as Glandula Infundibuli, is not 
a gland but a sensory organ reacting on a distinet stimulus, it 
seemed to be of importance to study Amphioxus lane. in this direction. 
The brain cavity of Amphioxus used to be figured as a pear-shaped 
enlargement of the central canal, provided oniy with the hollow 
prolongation beneath the bottom of the olfactory groove, discovered 
by LANGERHANS. 
In the first part of his “Studien zur Entwicklungsgeschichte des 
Kopfes der Kranioten”!) Kuprrer for the first time gave a detailed 
discription of this cavity and pronounced a distinct homology, based 
on anatomical facts, between the brain of tho higher vertebrates and 
the brain cavity of Amphioxus. He came to the conclusion, that the 
ventricle of the brain of Amphioxus is homologous, not with the 
fore-brain (“Vorderhirn’”) of the Craniata in its definitive form, but 
with the primary anterior part (“Vorhirn”) of the two parts in 
which the brain was seen to be divided in young Acipenser and 
Petromyzon embryos. 
According to KUPFFER the brain cavity of Amphioxus (lc. Fig. 22) 
is bounded posteriorly by a distinct folding or flexure of the ventral 
wall of the central canal; in front of this flexure there is to be 
seen a thickening of the wall, homologised with the tuberculum 
posterius; in front and ventrally of it the floor of the brain cavity 
is thinned out very much and forms a funnel-shaped cavity „der 
gebogen sich nach hinten unter dem Tuberculum posterius vorschiebt” 
(Le. Page 75). This funnelshaped cavity KuprreR homologises with 
the infundibulum of the higher vertebrates. In his somewhat schematic 
drawings no celldifferentiation whatever is to be seen; in front of 
the rather deep infundibular cavity and behind it the cells are 
somewhat spindleshaped and arranged in several layers, at the bottom 
of the infundibular cavity one layer of very flat cells may be 
distinguished. 
The results of my researches on adult and larval amphioxus did 
not coincide with Kuprrers account mentioned above. 
On median sections through large adult amphioxus specimens (fig. 1) just 
1) Heft 1. Die Entwicklung des Kopfes von Acipenser sturio an Medianschnitten 
untersucht. Miinchen 1893. 
46 
Proceedings Royal Acad, Amsterdam, Vol, IV. 
