Kappers, Teleostean and Selachian Brain. 27 



Bellonci, Herrick, Edinger, Krause and Catois. In the 

 section taken somewhat farther caudad (Fig. xxxvii) we observe 

 the ascending and descending loops of the commissura transversa, 

 the lower loop as a compact whole, the other higher up as a few 

 distinct bundles of which the most lateral are quite near to the 

 n. opticus. 



Here at the left, directly frontal to the corpus geniculatum 

 laterale, the optic nerve begins to divide into two parts, one more 

 lateral, the other more medial. (Herrick calls them the cephalic 

 and caudal; Krause the ventral and the medial; Mayser and 

 Bellonci the foremost and the hindmost or the upper and the 

 lower roots.) 



These, however, do not contain all of the opticus fibers. Imme- 

 diately under the fissure of the ventricle in the median line a small 

 bundle of opticus fibers has separated from the rest (Figs, x, xi, 

 xxxiv, xxxv). In Fig. xxv they are situated over the uppermost 

 decussating fibers of the commissura transversa. (Shown only 

 on the left of the figure. The tract on the right side escaped the 

 notice of the artist from the fact that it is colorless in the prepara- 

 tion.) In Fig. xxxvi they (together with a few fibrae ansulatae to 

 be mentioned later) join without decussation the commissura 

 minor Herrick, to be described later, and disappear at the outer 

 side of the tectum opticum (Fig. xxxviii). Mayser has already 

 observed this small medial bundle, but does not say anything 

 about its destination, nor could Krause reach any certainty as to 

 the character of these fibers. However, I can quite confirm 

 Bellonci's statement that ultimately they join the other opticus 

 fibers. In Rhodeus amarus, where as I suppose Edinger illus- 

 trates without naming them, they seem to advance far less deeply 

 into the thalamus. 



Proceeding caudad and observing chiefly the right half of the 

 'tween-brain and mid-brain roof, we see (Figs, xl, xli) far dorsad 

 and lying obliquely in the middle of the scarcely colored optic 

 tracts the highly developed strongly medullated brachium laterale 

 tecti. This tract originates from the tectum opticum and ter- 

 minates in the corpus geniculatum laterale (Fig. xlii), and not 

 being degenerated contrasts clearly in the field of the degenerated 

 opticus fibers, while on the left side it cannot be distinguished. 

 On the left side, however, where the fibers are not so compact 

 (Fig. xxxix) the much smaller brachnan mediale fecti is much 



