THE LEEOHES OF JAPAN. 355 
widening of the yellow stripes, but by replacing the olive- 
ground colour between these stripes with a brownish black 
almost as dark as the dusky borders of the stripes. This dark- 
ening of the ground-colour is equivalent to widening the six 
pairs of adjacent dark borders until each pair blends into a 
single dark stripe. The blending is not quite complete 
throughout, so that there still remains unmistakable evidence 
of the double origin of the dark stripes, especially in the inner 
of the two lateral ones of each side. It will be noticed by 
comparing figs. 11 and 18 that the segmental papille hold the 
same position relative to the stripes in both cases. A similar 
case of darkening the ground-colour is seen in figs. 15 d, 
and 20. 
An illustration of the third case, in which the two dark 
borders of the yellow stripe are brought together by the oblite- 
ration of the stripe, may be seen in fig. 16 d, which represents 
a portion of a Leech from Aomori; and again in fig. 17, a 
specimen from Tokio. In the Aomori specimen the external 
lateral yellow stripes have been completely effaced, the dark 
borders of each uniting to form a narrow dark stripe on each 
side. In the two inner lateral stripes, small remnants of the 
yellow are still to be seen at intervals. The median stripe is a 
bright lemon yellow, well preserved throughout, and accom- 
panied by the usual dark borders. Both specimens from 
Aomori show only mere shadows of the dark stripes bounding 
the yellow margins on the ventral side (figs. 15 and 16). In 
the specimen from Tokio, it is the two inner lateral yellow 
stripes that have been wholly effaced, while the external ones 
are preserved only at intervals. The median yellow stripe is 
here interrupted on the papillate rings ; it broadens as usual on 
the cephalic lobe, but does not extend to the acetabulum. 
Here the dark borders of the median stripe are very distinct. 
In fig. 14 is represented a, specimen in which the yellow 
stripes and their borders and even the ground-colour have 
faded. The stripes are barely indicated, and, contrary to the 
rule, the dorsal side is lighter than the ventral. 
The yellow stripes are rarely evenly continuous as in fig. 15, 
