18 HIRUDO. 
On the 13th of August several leeches had been committed to a 
cylindrical vessel of water, for the purpose of obtaming their capsules. 
One appeared in four days, which contained five specks. Two of these, 
however, proved either illusive or abortive ; but three of them, enlarging 
circularly at first, had become oval in the course of development, as 
embryos, within a week. Eleven days subsequent to the production of 
the capsule they extended and contracted ; yet neither external eyes nor 
internal organs were visible. They were of singular structure, the whole 
being formed as if by united vesicles or large globules ; all having some 
rotundity,—nothing angular. It could not be determined whether they 
were hollow. Two of the embryos were nearly equal; the third, between 
them, smaller. In a fortnight they occupied nearly the whole capsule ; 
and in eighteen days from its production very little of it remained free. 
In twenty days the lower half of the young appeared deeply corrugated, 
yet no segments were perceptible, neither could circulation of the blood 
be discovered. Quite a different character distinguished the upper half 
of the animal, in being perfectly smooth throughout, thus inducmg me 
to conclude the dark portions of the other to be intestinal. The eyes 
appeared as minute specks across the front of the upper surface. The 
surface of the skin had a reticulated aspect, and there were slight remains 
of the vascular structure above described, fig. 14 ; one of the embryos 
enlarged, fig. 15. No other motion than simple contraction and exten- 
sion was then sensible. 
Two having attained maturity forsook the capsule thirty days after 
it was deposited ; the third, testifying much activity, escaped two days 
later. 
Thus, in August and September, the eight-eyed leech comes to ma- 
turity in thirty or thirty-two days after production of the ovum con- 
taining it. 
The young leeches on exclusion extend to about the third of an inch, 
and are of pale amber colour, swim actively amidst the element, and 
adhere by the sucker in the course of the day. 
It is of the deepest interest to the reflecting mind to watch the pro- 
gressive evolution of matter from the moment the dormant spark of life 
