158 STRONG. [Vol. X. 



ad facialem of the tadpole. Its manner of union with the VII 

 is also similar to that in the tadpole. A further study of this 

 nerve in these forms is desirable, especially as it is stated that 

 this branch does not exist in Menobranchus; and yet the R. 

 jugularis has some fine cutaneous twigs. Naturally, Fischer 

 does not distinguish between the cutaneous nerves belonging 

 to this component and those belonging to that next described. 

 From what has been shown, however, there is reason to believe 

 that the cutaneous fibres accompanying the motor branch to 

 the M. mylohyoideus posterior belong to the former, i.e.y to the 

 general cutaneous component. 



2. Special Cutaneous or Lateral Line System. 



a. Comparison with other Amphibia. — The second component 

 has been designated, in contradistinction to the preceding, 

 the ^^ special cutaneous'' component. It includes VII (^) and 

 IX + X (<^). Inasmuch as it is distributed to the lateral sense 

 organs of head and trunk it may also be called the * lateral 

 component.' 



This component is in many respects a remarkable one. Its 

 internal origin or, rather, termination is in certain tracts (and 

 nuclei, Osborn) immediately dorsad to those constituting the 

 origin of the Auditory. These tracts do not seem to be in any 

 way directly continuous with spinal cord tracts as is the case 

 with the ascending Trigeminus. The origin of this component 

 composes, apparently, then, a structure peculiar to the medulla 

 oblongata. The fibres are large and present considerable uni- 

 formity in size. This component has evidently a constant and 

 definite distribution, viz.y to the lines of sense organs ranged 

 along the head and trunk of the tadpole. The arrangement of 

 these branches and their ganglia has already been described; 

 one point may be here added, namely, that the ganglion cells 

 are not very numerous and do not usually seem to produce any 

 strongly marked ganglionic swelling. There are not, however, 

 very many fibres in these nerves in the tadpole, a fact which 

 accounts for the peculiarity above mentioned. Besides this, its 

 ganglion cells are possibly bipolar (comp. Stannius, 57). 



