THE LEECHES OF JAPAN. 337 
Land Leech this body is band-shaped and bent in various direc- 
tions, so that in section it often appears to consist of several 
separate pieces, which may be straight, bent, or looped. The 
optic nerve does not enter the eye at its base, but at some 
little distance from the base on the anterior side. 
The clear central cells of the eyes are very remarkable ele- 
ments, differing in their general appearance and structure very 
conspicuously from any cells that have hitherto been dis- 
covered in other parts or organs of the Leech. But I have 
found that these peculiar cells—from two to four or more in 
number—are also present in each of the segmental papille of 
the ventral as well as of the dorsal side, in both land and 
aquatic Leeches. I have succeeded in tracing a nerve up to 
these cells, without, however, finding any connection. As 
before stated, the lead-coloured dots at the centres of the seg- 
mental papille are free from pigment and transparent like the 
epidermal cap of the eye. The only important difference in 
composition between the eyes and the papille is the absence of 
the pigment layer in the latter. This difference is not easily 
reconciled with the view that these papille are ocular in cha- 
racter. Still the fact that they are much larger on the dorsal 
than on the ventral side, and the presence of those “ peculiar 
(sense ?) cells ” situated just below a window-like opening in 
the surface pigment, as well as their obvious serial relationship 
with the eyes, favour such an interpretation. The evidence 
pointing in this direction is, perhaps, somewhat weakened by 
the fact that those same clear cells, which have hitherto been 
regarded as peculiar to the eyes, are found alongside the 
nerves running to the “ goblet-shaped”’ sense-organs located 
in the margin of the cephalic lobe. The presence of these 
cells in the segmental papille cannot therefore decide the 
question of their physiological significance. It is quite cer- 
tain, however, that these papille are not respiratory organs, 
as suggested by Ebrard. Their position is not in favour 
of their being organs of taste or smell; and their structure 
is opposed to the idea that they are either auditory or tactile 
organs. 
