686 The American Naturalist. [August, 
The histological details of the apparatus Tt. are shown in figure II 
as they appear viewed with a 72 inch oil immersion lens giving about 
1000 diameters. While the columnar epithelial cells lining the tenta- 
cular canal Ce are not so regular as one sees in a functional organ yet 
they are so well defined, especially in the lower portion that the ob- 
server cannot be misled as to their identity. The nucleus is visible in 
about one half the cells and the nucleolus is apparent in many cases. 
In the upper portion the cells have lost their nuclei and are in a degen- 
erate condition. rt is a cross-section of a muscular element which I 
believe is the atrophied remains of the muscular retractor of the 
tentacle. In my preparation, only the bony and muscular tissues have 
taken on the very light shade of red which characterizes rt. Since the 
latter is certainly not a bone, I infer it must be a muscle, and if a muscle 
what other function could it have had than to retract the tentacle. 
This muscle is visible in ten consecutive sections while the canal Ce 
appears in greater or less completeness in thirteen sections. The black 
dots of various sizes seen irregularly distributed throughout the gland- 
ular tissue ObD may possibly be nuclei as they are stained a deep red 
or they may be scattered nerve fibres whose connection with the ramus 
maxillaris on its branches I have not been able to demonstrate because 
the degenerate glandular tissue was so loose as to be displaced in several 
sections. The irregular wavy lines, I think represent cell boundaries. 
These are visible with an enlargement of two hundred diameters in the 
lower portion but can scarcely be seen with an oil immersion immedi- 
ately beneath the canal. ITts is the inner tentacle sheath composed of 
connective tissue fibres. It is clearly seen in eighteen consecutive sec- 
tions. ATts represents the outer tentacle sheath which with a low 
power can be seen in twenty-five consecutive sections. Thus it is ob- 
served that this tentacular apparatus is about one millimeter long lying 
below and external to the eye. 
The tentacular canal is complete in only four sections. Figure IIT 
represents the fourth section posterior to figure II. The columar epi- 
thelium has disappeared on the dorsal side where the inner sheath enters 
and on one side lies close to the wall, while on the other it mingles with 
a loose tissue T which may be the remainsof a tentacle. This tentacle 
is prominent in six sections, in three of which the canal is complete so 
that the inner sheath does not enter it. The lumen of the canal varies 
but slightly in size. The musculus retractor rt dwindles as we pass 
anterior or posterior of the section shown in figure II. The glandular 
tissue decreases both anterior and posterior to the median section. The 
portion on the ventral side persists the longest, being present in thirteen ` 
