130 



THE ANCESTRY OF VERTEBRATES 



As shown also by HATSCHEK's instructive figure of the 

 head of Amphioxus, reproduced here as fig. 26, there is a 

 dorsal spinal nerve between every two myotomes. It belongs 



^-AT? 



Vd. 



Fig. 26. Head of Amphioxus, from the left side, after Hatschek 

 1892, p. 143 (nomenclature altered). 



A,B,C, etc. segmental nerves belonging to segments 1,11, III, etc. 



a, anterior branch of the first segmental nerve ("AT. ophthal- 

 micus prof unaus"), Ch. notochord, cu, prof, sup. branches 

 of the segmental nerves, fl. rest of the neuropore, NR. 

 nervus recurrens to the branchial plexus, r. pr. I rostral 

 prolongation of the first somite, S. Hatschek's groove, T. 

 tentacles (cirri), Vel. velum, I, 11, 111 etc. myotomes. 



