520 



earlier stage ^), when the motor nerve-trunk is a strand of protoplasm 

 perfectly continuous with the protoplasm of the myotome. 



The discussion of the great significance of these facts would hardly 

 be relevant to the main purpose of this communication. But I may 



remark in passing 



Lamina tcrmiiialis 



Nasal Sac 



X 



' Cerebral 



Hemisphere 



Thalam- 



encephalon 



Fig. 4. 



Fig. 5. 



that, as the olfactory 

 nerve retains in a 

 m uch larger measu re 



Figures 4, 5, 6 

 and 7. Fig. 4 is a dia- 

 gram to explain the 

 features of Fig. 5, which 

 is the photograph of a 

 horizontal section (93 ß, 

 2.1.5) of a foetal Lepi- 

 dosiren (Graham Kerr's 

 stage 30). 



The circle z marlis 

 the area of the left cere- 

 bral hemisphere and 

 nasal sac, M'hich is re- 

 presented ou an enlarged 

 scale in the photograpii 

 shown as Fig. 6. 



Fig. 7 is a drawing 

 (made with camera lucida, 

 using the Zeiss D) of 

 the connecting bridge x 

 (Fig. 4) and the adjoining 

 parts of the right nasal 

 sac and cerebral hemi- 

 sphere. [The drawing 

 was not made from the 

 section shown in Fig. 5, 

 but from a neighbouring 

 one in the same series, 

 93 ß, 2.1.3.] 



In Fig. 4 y refers 

 to the Lamina chorioi- 

 dea, the attenuated band 

 joining the thahuncn- 

 cephalon to the cerebral 

 hemisphere. 



1) On Some Points in the Early Development of Motor Nerve Trunks 

 and' Myotomes in Lepidosiren paradoxa (Fitz.). Transactions of the 

 Boyal Society of Edinburgh, Vol. 41, Part 1, No. 7. 1904. 



