523 



the front part of the hemisphere (Fig. 8 A). As development proceeds 

 this inflated tuberculum olfactorium becomes still bigger and the ol- 

 factory nerve becomes considerably elongated so as to produce the 

 bizarre arrangement exhibited in Fig. 9. 



[Figures 8, 8' and 9 were each made by superimposing a number 

 of camera-lucida outlines of serial sections one on top of the other 



A 



Bulbus 



ollactorius 



Thalam- 



encephalon 



Thalam- 

 us Nasal Sac encephalon Bulbus olfactorius 



Cerebral 

 Hemi- 

 sphere 



Mes- 

 encephalon 



Nervus 

 olfactorius 



Fig. 8. 



on one sheet of paper. This 

 method was adopted because 

 the few days spent in Glasgow 



Fig. 8. A rough reconstruction of 

 part of the right side of the brain of 

 a larval Lepidosiren (Graham Kerr's 

 stage 30) seen from above. )x( circ. 30. 

 4 represents the large bulging of tuber- 

 culum olfactorium (Burckhardt's" Lo- 

 bus postolfactorius"). The olfactory nerve 

 passing from the nasal sac to the olfactory 

 bulb is not labelled. 



Fig. 8'. Lateral aspect of a brain 

 at the same stage. 



Fig. 9. A similar reconstruction 

 of the right side of the forebrain in an 

 older larva (Graham Kerr's stage 38). 



This reeonstruction was made from 

 the series of horizental sections disting- 

 uished as 140 H. Some of the contour 

 lines employed in making the drawing 

 have been allowed to remain in the 

 region of the olfactory bulb and hippo- 

 campus to illustrate Lhe method of practis- 

 ing of this rough mode of reconstruction. 



Fig. 8'. 



Thalam- 

 encephalon 



Nasal Sac 



Nervus 

 olfactorius 



Bulbus 

 olfactorius 



Hippocampus 

 Fig. 9. 



on this task did not afford a sufficient length of time for more complete 

 reconstructions, and, as Graham Kerr had already published (op. cit. 

 supra) drawings made from careful reconstructions, the risk of any 

 serious inaccuracy in my drawings was thereby obviated.] 



