16 HIRUDO. 
Seven having been taken and consigned to a vessel, I found one of them 
soon after attempting to swallow the Hirudo stagnalis, which, though of 
small dimensions, seemed too large for its gullet. The head of the prey 
is first absorbed ; and, as all predacious animals apparently employ a 
definite mode of attack, this may be the best way of defeating resistance. 
As if in just retaliation, the eight-eyed leech is itself the victim of others 
of its more powerful kindred. In the natural state it seems to subsist 
also on the succulent plants, and on decaying wood, but always preferring 
animal substances. Though feeding copiously in confinement, its size 
declines progressively ; the excretions are in the form of long thickish 
spiral threads. 
This species is very extensively diffused in Scotland. It is found 
in lakes, ponds, streams, and marshes. The quality of the specimen de- 
pends much on the abundance of food, and the facility of retreat. Many 
dwell on aquatic plants, or oceupy the under surface of stones. If a 
quantity of the former be pulled up, and heaped on the ground, the 
leeches soon quiting their haunts descend as if in quest of shelter, when 
they will be readily found on the earth below. They seem always to 
retreat downwards. 
From the facility of procuring and preserving the Hight-eyed Leech 
it is particularly convenient for observation. But the labours of the 
naturalist are commonly abbreviated by casualties, especially the sus- 
ceptibility of disease, which few specimens escape. The sucker and whole 
lower portion become motionless, and covered with mould, so that the 
upper half is living while the under is dead. Perhaps the temperature 
of an apartment is too high, or so different from its wonted dwelling as 
to prove pernicious. 
No species is more adapted for shewing the progress of the embryo, 
from the moment it becomes visible until fair maturity, and issuing forth 
in perfection from the ovum of the parent. 
This is properly a capsule, with an integument, not a shell, and of a 
brownish-yellow colour ; the longitudinal segment of an ovoid, smooth 
and convex. The longest capsules extend about two lines and a half, 
by somewhat less in breadth. The longer axis is always parallel to the 
