The nucleus of BELLONCI in birds - DWC

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by H UBER and CROSBY (their component from septo-mesencephalic system
to habenula).
The tractus oHacto-habenularis lateralis is not reported here for thc
first time for birds, it was described in them long ago as tractus striohabenularis
by MÜNzER and WIENER (1898) and EDINGER and W ALLEN­
BERG (1899). Also KAPPERS and THEUNISSEN (1908) mention th is bundIe.
Medial to the nucleus of BELLONCI and coextensive with its caudal haH
lies a cell mass, which is closely applied to the dorsal peduncle of the
lateral forebrain bundIe (figs. 5, 6). At its beg inning it only covers the
lateral aspect of the lateral forebrain bundIe, but gradually it expands
medially so as to cover this bundIe dorsolaterally too. Also in the sparrow
this nucleus is present, but here it lies farther backward (fig. 7). No doubt
this is the crusta peripeduncularis of EDrNGER and W .ALLENI3ERG (1899),
which cell mass is only referred to of later authors by GROERBELS (1924),
who in the dove and chick is inclined to identify it with his geniculatum
laterale tertium anterius 1) and by RENDAHL (1924, p. 315), who could
not find it in the chick. It may be the same as the bed nucleus of the
tractus thalamo-frontalis medialis of HUBER and CROSBY (1929, p. 89).
I suppose this cell group to be the interstitial nucleus of the stria
terminalis 2), on the ground that it occupies exactly the same position
relative to the lateral forebrain bundIe and nucleus of BELLONCI as the
latter does in crocodilians (compare figs. 5 and 6 of the dove with fig. 2d.
of Crocodilus porosus in the previous paper).
We shall now put forward our arguments for regarding the nucleus
lateralis anterior of birds as the homologue of the nucleus of BELLONCI
of amphibians, reptiles, and mammals.
In the first place the position of the two nuclei is quite similar, both
being situated in the foremost part of the thalamus, dorsal to the oral
extremity of the ventral lateral geniculate, with the restriction, however,
that in anures the nucleus of BELLONCI has shifted rather caudad along the
dorsal side of the lateral geniculate (AODENS, 1938, fig. 1). In mammals
the nucleus of BELLONCI occupies its usu al rostral position, hut here the
lateral genicuJate has shifted caudad, so that there is a gap between
these nuclei.
As to the development of the nuclei, we are comparing, the nucleus of
BELLONCI is known to arise from the ventral thalamus (see ADDENS, 1938).
About the development of the nucleus lateralis anterior of birds RENDAHL
(1924) and KUHLENHECJ( (1937) unfortunately are at variance. According
to RENDAHL (1924), in the chick this nucleus splits oH from the foremost
1) This is not correct. Both in the dove and chick the crusta peripeduncularis lies
farther forward and more medially than GROEBBELS' geniculatum laterale tertium anterius.
In my opinion the latter is the foremost dorsal part of the tectal gray of HUB'ER and
CROSBY (1929).
2) In the previous paper, following CAIRNEY (1926) for Sphenodon, I labelled th is
nucleus as the interstitial nucleus of the tractus amygdalo-praeopticus.
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