LATERAL LINE SYSTEM OF|cHnL^:RA COLLIEI 
365 
16 
Fig. 15 A diagram to illustrate the arran'^emsnt of the cartil i^;? rings of tlie 
canal, described in the text. 
Fig. 16 A transsection through the entirj animal near the tip of the tail. 
thickens and passes across the floor of the canal as a stratified 
epithelium of ten or more layers. Along the median line of the 
floor of the canal this thickened epithelimn becomes modified to 
form the sense organs. These sense organs are segment ally ar- 
ranged, but there is, apparently, no very sharp line to be drawn 
between the ordinary epithelium of the floor of the canal and 
that which is modified into sensory epithelium. 
At intervals of about one to two centimeters the epithelium 
of the floor of the canal is especially thick and is modified to form 
the sense organs, while between these organs the epithelium is 
of varying thickness, at the thinnest being but little thicker than 
that of the outer parts of the canal described above. Between 
the epithelium of the bottom of the canal and the fibrous rings is 
