525 



presenting a very close resemblance to that of Lepidosiren, which I 

 have shown in Fig. 8'. Bing also, in his part of the monograph on 

 the brain of Ceratodus, which was written in conjunction with Burck- 

 HARDT, represents (Fig. 13, p. 549) and describes the brain of a larval 

 Ceratodus (stage 48) in the same phase as that described by Sewertzoff 

 (Fig. 4): but there is as great a discrepancy between their two inter- 

 pretations of the Ceratodus-brain as there is between my identification 

 of the parts of the hemisphere in the Dipneumona and that adopted by 

 BuRCKHARDT and Bing. 



Sewertzoff's identification of the various parts of the foetal 

 Ceratodus-brain agrees with the account I have given (supra) of the 

 foetal Lepidosiren-brain (Figure 8'). 



But Bing applies the name "Lobus olfactorius" to the structure, 

 which Sewertzoff and I regard as the tuberculum olfactorium. [Se- 

 wertzoff uses Burckhardt's term "Lobus postolfactorius", which, 

 for reasons explained above, I have homologised with the tuberculum 

 olfactorium.] Bing, however, makes a vigorous attack on Sewertzoff's 

 contention (p. 550), in the course of which he makes the following 

 statement : 



"Außerdem aber sind an seiner Figur das Vorderhirn irrtümlich 

 als Lobus olfactorius, dieser aber als Lobus postolfactorius bezeichnet, 

 obgleich er schon seiner äußeren Lage nach diesem von Burckhardt 

 bei Protopterus unterschiedenen Höcker nicht entsprechen kann. 

 Ungenau ist auch der Verlauf des Olfactorius wiedergegeben." [Se- 

 wertzoff presents a diagram of the course of the olfactory nerve in 

 the larval Ceratodus exactly like analogous to that shown in my Fi- 

 gure 8'.] "Zugleich mit der falschen Homologisierung der Abschnitte 

 des Vorderhirns verbindet ihn Sewertzoff dorsal mit dem Vorderhiru, 

 das er für den Lobus olfactorius hält. In Wirklichkeit strahlen die 

 Olfactoriusfasern von der Riechschleimhaut über die ganze ihr zuge- 

 wandte Calotte des Lobus olfactorius in Gestalt von Faserbündeln 

 aus" (p. 550, 551). 



Not having seen the actual brain of Ceratodus it would be rash 

 of me to intervene in this dispute. But there are two facts which 

 seem to me to indicate that Sewertzoff has the right on his side: 

 1) it is hardly conceivable that he could, by an effort of the imagin- 

 ation, have drawn an olfactory nerve pursuing such a bizarre course 



von Ceratodus Forsteri in Semon's Zoologische Forschungsreisen in 

 Australien und dem Malayischen Archipel, 1905 — see Fig. 2, p. 523, 

 Fig. 5, p. 535 and Taf. 42; and Fig. 13, p. 549. 



