Kappers, Teleostean and Selachian Brain. 45 



question I may say that, though I am quite sure that the functions 

 belonging to these tracts are homologous, it certainly may be that 

 in the same pallial region of the selachians there are still other 

 functions not in direct relation with the tracts in question which 

 may be absent in the lobi anteriores of the teleosts. The functions 

 to which I refer are the cortical functions, which, as Johnston 

 correctly pointed out, are related to higher tertiary connections 

 and which must be studied by Golgi preparations. Though it 

 would have been very interesting to investigate this question, 

 time did not permit me to take it up and I hope that some one else 

 will do this, as Johnston has already done for the ganoids and 

 BoTAZZi partially for the selachians. 



Now, we pass to the description of the commissures and decussa- 

 tions of the praeinfundibular part of the 'tween-brain, of which I 

 have already mentioned the most ventral one, the decussatio tr. 

 pallii. The remaining decussations found here and not yet men- 

 tioned are those of the opticus fibers and the commissura trans- 

 versa. 



As far as my series of sections show, the opticus fibers seem to 

 decussate wholly both in Galeus and in Angelus squatina. This, 

 of course, could be settled for certain only by experiment. After 

 their decussation the opticus fibers go between the mantle bundle 

 and the commissura transversa in the direction of the corpus 

 geniculatum laterale (Fig. lix), under which a part goes as the so- 

 called ventral or lateral opticus root, while the other part goes 

 into the medio-dorsal region of the tectum opticum. As for the 

 hrachia tecti, about which, when treating of the teleosts, I was able 

 to give such positive information, I can only mention here that 

 the corpus geniculatum is supplied with fibers from the tectum. 

 This group of fibers may be recognized in Figs. Ivi and Ivii. The 

 section first mentioned is taken more frontally than the second, 

 so that perhaps the first one shows the entering of the brachium 

 anterius, the second that of the brachium laterale or posterius. 

 This, however, is only a possibility; certainty in this matter could 

 be obtained only by degeneration experiments. 



Now, I have still to describe the third praeinfundibular decussa- 

 tion, the commissura transversa, situated dorsal to the optic decus- 

 sation, the course of whose fibers is clearly to be seen in Figs, lix 

 and Ix, anterior to the commissura pallii. This commissure, 

 which is but little developed in Angelus squatina, cannot be fol- 



