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 ^wo, cephalic and 

 mid-thoracic. 



