25 
on the Hirudo vulgaris. 
About the middle of June, several capsules were deposited. 
As some of them were transparent, I had an opportunity of 
examining their contents. I could distinctly observe the ova 
in them; then had the satisfaction of identifying animal 
existence ; and ultimately, of tracing the young from this 
period to their exclusion. 
Having thus found the ova productive, I examined the 
vessel daily, with a view of marking the time when they 
were deposited, and the period required to produce the 
changes I have noticed. 
On the 4th of August, I observed a capsule, in which the 
ova were very distinct .* on the 26th of the same month* 
animal existence was developed, and on the 17th of September 
the young were excluded. In this instance, signs of vitality 
were manifest in twenty-two days, and in forty-four days, 
the young had escaped. 
On the 14th of August, another capsule was deposited, in 
which animal existence was evident on the ist of September, 
and on the 24th of the same month, the young were excluded. 
In this case, the first sign of life was traced in eighteen days, 
and the young had escaped in forty-two days. 
August 13th. I observed two of the H. vulgaris in actw 
coitus , and found them to copulate after the same manner as 
the common snail, In this state I removed and kept them 
apart from: the rest. On the following morning they had 
separated, when I consigned them to different vessels. One 
of them, shortly afterwards, escaped from its, confinement, 
and was lost. It, however, produced two capsules, one on 
the 17th of August, the fourth day after copulation, and the 
other on the 18th both which proved unproductive. The. 
