252 CLAP p. [Vol. XV. 



channels of the dermal bones and only primary pores are 

 present. 



Innervation. — The dorsal branches of the VII and X cranial 

 nerves supply the lateral line system. The supraorbital line 

 of organs are innervated by the R. ophthalmicus superfacialis ; 

 the infraorbital by the R. buccalis facialis ; the operculo-man- 

 dibular by the R. mandibularis externus; while the vagus sends 

 branches to the single canal organ in the temporal region, as 

 well as to the organs on the top of the head. 



The anterior organs of the trunk are supplied by the R. re- 

 currens of the VII, which forms an anastomosis with a branch of 

 the vagus just outside of, and posterior to, the auditory capsule, 

 and extends on to the body, occupying a position directly super- 

 ficial to the N. lineae lateralis. The R. recurrens in Batrachus 

 is probably the same as the R. dorsalis recurrens facialis (tri- 

 gemini) of the Siluroids, or of the cutaneous quinti in Gadus, 

 although following a different course on the side of the body. 



It remains for future investigation to determine the exact 

 innervation of the organs on the body of Batrachus. 



The complexity of the peripheral nervous system grows more 

 apparent with every step of advance in methods of investiga- 

 tion. In Kupffer's words, " The researches of the last decade 

 in comparative embryology have shown that the development 

 of the peripheral nervous system is a far more complicated 

 process than it was formerly supposed to be" (36). This 

 is especially true in the case of the vertebrate head, as the 

 recent work on Amphioxus by Hatschek (37), and the important 

 investigations by Kupffer (38) on Ammocetes clearly show. 



In the views of Hatschek (37) we encounter a slightly modi- 

 fied form of Balfour's hypothesis in regard to the origin of 

 both cranial and spinal nerves from a type of segmental nerves 

 which had only dorsal, yet mixed dorsal roots. According to 

 Hatschek the spinal nerves have lost certain elements, while the 

 cranial nerves have retained more of the primitive characteris- 

 tics. In Petromyzon, Kupffer (38) has shown that the "dorsal 

 spinal nerve root " and the " mixed head nerve root " exist 

 together side by side as coordinate components of a typical 

 head nerve. 



