( 58 ) 



pared with special parts and stages of development of the brain of 

 craniote embryos. 



After these statements I will add a few words concerning the 

 cranial or rostral part of the cerebrum and the adjacent organs. 



In his paper of 1906 Edinger describes a new organ, the "frontal 

 organ", lying in front of the brain and being innervated by a special 

 nerve. I regret to say that I (no more than Wolff in his paper of 

 1907) could find no trace of a frontal organ. Even after a most 

 careful study of a number of individuals I can only find in the 

 rostrum the often queerly shaped irregular mucous canals (Sehleim- 

 canale) lying ventrally and dorsally of the chorda. They are never 

 connected with the epidermis, bul all receive very thin nerve-fibres 

 from the first cerebral nerve. 



Although the existence of a distinct nerve connecting the olfactory 

 groove of Kölliker with the brain, is denied by Edinger, I could 

 find it in my preparations as a bundle of fine nerve-fibres, connecting 

 the sensory cells of the groove with the dorsal part of the brain. 

 In all respects I could affirm the exact observations of Dogiel (1903; l ) 

 both concerning the sensory cells in the olfactory groove and the 

 nervous connection of them with the brain. 



In the dorsal part of the cerebral wall I find a distinct commis- 

 sural system, wherefrom bundles of nerve-fibres curve backwards 

 (much like the fasciculus retroflexus of the commissura posterior of 

 the craniotes) and a few fibres curve round forward. There are 

 more systems of fibres to be found in the wall of the cerebral vesicle, 

 but they are rudimentary and composed of only a few fibres. This 

 is not the place to enter into details about these things. But when 

 we take all this into account I think it is not permissible to consider 

 the amphioxus-cerebrum as an "archencephalon" (Kupffer), that has 

 remained on a very low stage of development, but we must regard 

 it as a degenerated cerebral system, which has become rudimentary 

 in many of its parts, a brain which has many of the features of the 

 brain of the ichthyopsides, but there are entirely lacking the organs 

 of the side-line system (lens of the eye, ear, side-line) and because 

 of that and of the fact, that the head has not developed as in the 

 higher vertebrates, it is degenerated and rudimentary. In connection 

 with this and with the elongation of the chorda the foldings of the 

 cerebral vesicle do not appear. Even a plica ventralis does not exist. 

 The infundibular organ remains in the niveau of the ventral cere- 

 bral wall. 



Leiden. Histological part of the Anat. Kabinet. 



~~ i) Anatomische Hefte 21. B«l. 1903. 



