tlie vertebral centra on the ventral side of the band of connective tissue which 

 separates the dorsal and ventral lateral muscles. From this position it sends off nerves 

 which supply the sense-organs of the dermal canal of the lateral line. At its origin 

 this nerve gives off on each side a branch which curves upwards and forwards and runs 

 immediately beneath the skin along the course of the supra-temporal dermal canal on 

 the right side, the series of supra-temporal superficial sense-organs on tlie left side. 

 On the left side there is another nerve given off from the lateral nerve at its origin : this 

 nerve runs immediately beneath the skin straight forwards across the side of the lateral 

 ridge of the skull : it supplies the superficial sense organs of the epidermis which lie 

 aloncf this direction. The two nerves last mentioned are shown in PI. XV, 2, indicated 

 as X 6a and X 6b. 



PI. XV, 2, exhibits the cutaneous branches of the cranial nerves on the left side, and 

 is intended to show the great development of these branches which has taken place in 

 connection with the numerous tactile filaments and epidermic sense-oi-gans which have 

 been developed on the skin of the left side of the head. 



