THE NERVOUS SYSTEM 



429 



its extreme shortening- of the cord, exhibiting but ten pairs of 

 spinal nerves, is not to be compared with Man, in which there 

 are more than thirty, but with the long-bodied salamanders, 



B 



FIG. 119. Nervous systems of invertebrates, showing the principle of 

 concentration. [A, from LANG, after OUDEMANS; B and C after LOWNE.] 



(A) Nervous system of the myriapod Lithobius, showing a connected chain of 

 approximately equal ganglia. (B) Nervous system of the larval Chironomus, the 

 " harlequin fly," showing a long chain of ganglia as in A. (C) Nervous system 

 of the adult Chironomus, with all the ganglia concentrated into two, cephalic and 

 mid-thoracic. 



