NERVOUS SYSTEM OF SCORPION. 



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central columns of Police, 

 as these columns cannot be 

 distinguished in the first 

 neuromere. 



Stage 8 . (Fig- 9-) The 

 changes that have taken 

 place since the preceding 

 stage are slight, and may 

 ' : t^> be easily seen by compar- 

 |^^ ing Figs. 7 and 9. It may 

 be noted that the fifteenth 

 nerve center has shifted to 

 the sixteenth segment, the 

 seventeenth nerve center to 

 the eighteenth segment, 

 and that the eighteenth, 

 nineteenth and twentieth 

 nerve-centers lie in the 

 nineteenth segment. 



Stage 9. ( Fig. 10. ) 

 This represents the embryo 

 at the time of birth. The 

 definitive outer form has 

 been attained but the gang- 

 lia are proportionally larger 

 FIG. 10. Ninth stage (at the time 

 of birth), X 34- Drawn with the 

 camera lucida from two cleared pre- 

 parations, and compared with dis- 

 sections and series of sections, ab 2 , 

 second abdominal appendage form- 

 ing the genital opercula ; ch, chel- 

 icera ; /.base of pedipalp ; / ] *, 

 bases of walking legs ; 12 20 , 

 twelfth to twentieth neuromeres ; 

 12-19, twelfth to nineteenth body 20 



segments. 



FIG. ii. Tenth stage (adult), 

 X 7- Camera lucida drawing of a 

 dissection from the dorsal side. 

 12 ~ 20 , twelfth to twentieth nerve 

 centers ; 16 ~ 20 , sixteenth to twen- 

 tieth body segments. 



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