228 RALPH EDWARD SHELDON 
laterad, and thence caudad into the tuber cinereum, and terms 
the tractus praethalamo-cinereus. Goldstein traces fibers from 
the pars magnocellularis caudo-dorso-laterad into ‘Das _ post- 
habenulire Gebiet,’ the ‘Liangsbiindel des grosszelligen Kerns 
des zentralen Hoéhlengraues.’ From the pars parvocellularis a 
few fibers decussate ventrally to enter the nucleus of the opposite 
side, the ‘Commissur des kleinzelligen Kerns,’ evidently the fune- 
tional equivalent of the commissura anterior, pars preoptica, 
previously described (fig. 188). He also finds other fibers 
which turn caudo-lateral, dorsal to the chiasma and postoptic 
commissures and end among the cells of the caudal portion of the 
nucleus in the rostral part of the hypothalamic wall. These 
fibers lie lateral to the fibers from the pars magnocellularis, and 
mesal to the lateral forebrain bundle. Goldstein believes that 
they constitute “‘ein Lingscommissur der einzelnen Abschnitte 
des kleinzelligen Kernes des zentralen Hohlengraues.”’ He like- 
wise believes that these fibers are identical with the tractus prae- 
thalamo-cinereus of Kappers and the caudal fibers of Johnston in 
Acipenser. Bela Haller finds a part of these fibers, but believes 
that they are connected with the optic apparatus. 
It was pointed out earlier that in the carp there are four differ- 
ent habenular connections from the nucleus preopticus, corre-: 
sponding partly to the connections described by Johnston in Aci- 
penser and Petromyzon. Olfactory fibers of the second order 
may be traced into both the pars parvocellularis anterior and pars 
magnocellularis, from the tractus olfactorius medialis, pars later- 
alis, just before its decussation. This agrees with Johnston’s 
conjecture (figs. 137, 139, 141). Unmedullated fibers arising from 
cells in the nucleus medianus and pars commissuralis of the pre- 
commissural body respectively also extend caudad, placing these 
two areas in relation with the different parts of the nucleus preop- 
ticus (fig. 140, tr. med. preopt. pars ant. and tr. med. preopt., pars 
post.). The fibers of the tractus mediano-preopticus, pars ante- 
rior pass caudad, ventral to the crossing bundles of the anterior 
commissure (figs. 37,54). From it and from the tractus mediano- 
preopticus, pars posterior fine fibers pass ventrad to end in either 
