( 897 ) 
dispersion bands enveloping the absorption lines. How the systematic 
displacements of the Fraunhofer lines toward the red, the obliquity 
of the lines in the spectra of sun-spots, and some other phenomena, 
may be explained from this point of view, has been shown in former 
publications *). 
Anatomy. — “Notes on the trochlear and oculomotor nuclei and the 
trochlear root in the lower vertebrates’. By Dr. W. G. Herr. 
(Communicated by Prof. L. Bork). 
(Communicated in the meeting of January 28, 1911). 
In the course of the past year | made several observations regard- 
ing the oculomotor and trochlear nuclei and their roots, in Petro- 
myzon, Lophius, Gadus, Hippoglossus, Rhombus, Pleuronectes, 
Selache maxima and Scyllium Canicula. The results of my researches 
can be best demonstrated by comparing the relations of the said 
nuclei in Petromyzon, Selache, and Lophius. 
RAT 
| E Nu IW 
Nu. HI. 
7 ? — / 
GD ZE 
Ril RL m aa 
Fig. t. Petromyzon. 
Fig. 1 shows the topographie relation of the oculomotor nucleus 
and root, the trochlear nucleus and root and the motor V and VII 
root in Petromyzon. 
As will be seen from this figure, the oculomotor nucleus in this 
animal lies partly on the level of its root-entrance, partly behind. 
The principal nucleus (Fig. 7), the only III nucleus according to 
some investigators, lies with its dorsal edge not far from the aquae- 
duct. Whether the so-called “ventral II] nucleus” be a III nucleus 
or not, I will not state positively. Its topography speaks strongly 
for this view, as can be seen in Figs. 1 and 6. The cell-type is, 
however, somewhat smaller than that of the dorsal nucleus. I have 
not been able to obtain sufficient certainty about the course of its 
axis-cylinders to enable me to decide this question. *) 
1) Proc. Roy. Acad. Amsterdam, XII, p. 266 and 466 (1909); XIII, p. 2 (1910); 
Les raies de Fraunhofer et la dispersion anomale de la lumière. Le Radium, 
t VIT Oct: 1910. 
2) This cellgroup is regarded by Auteorn, Jonnsron, and Scuitume as being a 
part of the IL nucleus, but by TRetsaxorr, on the other hand, as a cell group 
independent of the oculomotor. 
