234 



last edition of the Vorlesungen (1908, p. 194, 195) speaks of the long 

 "praethalamus" in Chiraaera which connects the thalamus with the 

 small telencephalon. That he includes the praethalamus in the dien- 

 cephalon is clear from the plate illustrating the phylogeny of the cere- 

 bral cortex in his latest book^) where the word diencephalon is printed 

 on this part of the brain. Since the velum transversum is attached 

 to the brain wall just in front of the nucleus habenulae, what Edin- 

 GEE calls the praethalamus in selachians belongs to the telencephalon. 

 The same is true in Chimaera. The paraphysis is situated over 

 the posterior part of the so-called praethalamus and the velum trans- 

 versum is a relatively small fold of the tela behind the paraphysis. 

 Instead of praethalamus this region constitutes the telencephalon 

 medium. 



Kappers in his papers on the phylogeny of the forebrain com- 

 pares the brain of Chimaera with that of other fishes, but a very un- 

 fortunate error in the identification of an important brain tract in Chi- 

 maera detracts greatly from the value of his conclusions. Kappers and 

 Theunissen^) give figures of three transverse sections of the fore- 

 brain of Chimaera in which is shown the position of two tracts called 

 tractus taeniae and tractus pallii. The "tractus taeniae" starts far 

 forward medio - ventrally between the bases of the olfactory bulbs, 

 rises toward the dorsal surface around the rostral end of the brain 

 and runs caudad along the medio-dorsal and then dorsal margin of the 

 brain wall the whole length of the "praethalamus". The attachment 

 of the membranous roof which finds place along this margin is of 

 course the taenia and perhaps for this reason Kappers calls this tract 

 the tractus taeniae. But the term tractus taeniae as used by Edin- 

 ger and Kappers is synonymous with tractus olfacto-habenularis and 

 the tract in question is so labelled by Edinger in a transverse section 

 of the "praethalamus" of Chimaera (1908, p. 195). Now if the nuc- 

 leus taeniae lay medio-ventrally between the olfactory bulbs in Chi- 

 maera it would be extremely difficult to make any comparison of the 

 forebrain of Chimaera with that of other vertebrates in all of which 

 the nucleus taeniae of Edinger and Kappers lies laterally, in the cau- 

 dal part of the evaginated lateral lobe or laterally and caudally in 

 those brains which are not evaginated. 



1) Edinger, L., Einführung in die Lehre vom Bau und den Ver- 

 richtungen des Nervensystems. Leipzig, 1909. 



2) Kappers, C. U. Ariens und W. F. Theunissen, Zur vergleichen- 

 den Anatomie des Vorderhirnes der Vertebraten. Anat. Anz., Vol. 30,^ 

 1907. 



