THE ANCESTRY OF THE VERTEBRATES 

 A, 



64: 



>-M 



ANDROCTONUS 



E. F AMMOCOETES G. 



Fig. 525. — Diagrams illustrating the hypothetical evolution of the vertebrate brair 

 from the nerve cord of a primitive arthropod such as Branchippus (fairy shrimp). 

 Supraesophageal ganglia are shown in solid black, prosomatic ganglia stippled, meso- 

 somatic cross-hatched. A, olfactory nerve; B, optic nerve; C, nerve to median eye; 

 P, prosomatic nerves; M, mesosomatic nerves. (Redrawn after Gaskell.) 



