238 JOURNAL OF COMPARATIVE NEUROLOGY. 
demonstration of the anatomical distinctness of the two chief 
types of special cutaneous sense organs and of their nerve 
supply. 
2. MeRKEL’s distinction between neuromasts (Verven- 
hiigel) and terminal buds (Exdknospen) will stand, the former 
being typically furnished with pear cells, or hair cells, which 
are shorter than the other cells of the sensory epithelium and 
which receive the specific nerve termini. To this structural 
difference we can now add the difference ‘in their innervation, 
the neuromasts always being supplied by nerves of the acustico- 
lateralis system, the terminal buds by communis nerves. 
3. Terminal buds are distributed over the entire cutaneous 
surface of the head and trunk, most abundantly on the _ head; 
but all are innervated from the communis component of the 
VII, IX and X cranial nerves, those of the trunk being sup- 
plied from the r. lateralis accessorius. 
4. There are four types of sense organs belonging to the 
acustico-lateralis system in Ameiurus (1) the organs of the 
internal ear, (2) the canal organs of the lateral lines, (3) the 
large pit organs, few in number and corresponding to the 
familiar pit organs of other teleosts in general and of Amia, (4) 
the small pit organs, not commonly present in other fishes, very 
numerous and distributed over the whole surface of the head 
and trunk. 
5. There is considerable conflict in the literature regard- 
ing the the exact courses of the lateral line canals in the 
siluroids. Accordingly I have plotted carefully the whole sys- 
tem in Ameiurus melas and have also examined by dissection 
portions of the system in several other American siluroids. 
There prove to be important variations in the different species, 
in different specimens of the same species, and even in the two 
sides of a single specimen. These differences include the pres- 
ence or absence. of a connection between the opercular and the 
main canals and the presence or absence of accessory ossicles 
at various points in the canal system, and may account for some 
of the disagreements in the literature. It follows that the de- 
tails of the lateral lines and their smaller accessory ossicles are 
