57 
been made to derive the brain of Craniates and its main 
peculiarities from the brain vesicle of Amphioxus. One of 
the best known is that of V. KUPFFER (1906, Il, 2, p. 13) 
who homologizes especially the archencephalon to the 
brain vesicle of Amphioxus, while the deuterencephalon 
is compared with the anterior end of the neural tube. The 
tuberculum posterius, a thickening of the floor of the Craniate 
brain over the plica ventralis which indicates the limit of 
arch- and deuterencephalon, is found again by V. KUPFFER 
in a group of ciliated cells in the floor of the brain vesicle 
of Amphioxus. These cells were first described by BOEKE 
(1902, p. 411) and termed by him the “infundibular organ”. In 
front of it KUPFFER (l. c. fig. 5, p. 7) even thinks he finds an 
infundibular depression comparable to the infundibulum of 
Craniates. BOEKE (1908), however, afterwards showed that 
such a depression does not exist. He sees the homologon of the 
infundibular organ in the sensory epithelium of the saccus 
vasculosus of fishes. A comparison of what WIEDERSHEIM 
says in the successive editions of his Comparative Anatomy 
about the homology of the brain of Craniates and the 
brain vesicle of Amphioxus shows clearly how opinions 
on this subject have altered. In the first edition (1883, p. 
2175) we read; “Durch die Lage und Ausdehnung der Cho: da 
dorsalis im Schädelgrund kann man a priori einen 
praechordalen und chordalen Hirnabschnitt 
unterscheiden. Jener sowie auch die zugehörige Schädelregion 
ist als ein späterer Erwerb und daher nicht einfach als 
transformirtes Rückenmark zu betrachten (GEGENBAUR). 
Daraus ergeben sich wichtige Consequenzen für das Gehirn 
von Amphioxus, wo ein praevertebraler Kopfabschnitt gar 
nicht zur Entwickelung kommt”, and p. 283: “Da die 
Chorda des Amphioxus sich bis zum vordersten Leibesende 
erstreckt, so kann auch, wie wir schon oben hervorgehoben 
haben, der darüber liegende Hirntheil nur dem chordalen 
Gehirnabschnitt der übrigen Vertebraten. . . entsprechen.” 
It is especially the comparison of the neuropore in 
Craniates and Amphioxus, one of the main arguments also 
of V. KUPFFER, which in the 2nd and 3rd edition induces 
WIEDERSHEIM to homologize the brain vesicle of the latter 
to the fore-, perhaps also to the mid-brain of Craniates, 
while in later editions he leaves the question undecided, 
saying: “Welchen Abschnitten des Gehirnes der Cranioten 
das Amphioxushirn entspricht, lässt sich nicht mit Sicherheit 
