Dr. Johnson’s observations 
16 
other leech produced a capsule on the 17th of August, the 
fourth day also after copulation, and one on each of the fol- 
lowing days : 18th, 21st, 23d, 24th, 27th, 30th, September 
4th and 8th: on the 2d of October, it died. In the whole it 
deposited nine capsules : of these, two only were productive. 
The one, (17th August) indicated animal existence in twenty 
days (6th September), and in fifty-six days (12th October), 
the young were excluded. In the other (August 18th), 
animal existence was developed in twenty-one days, (Sep- 
tember 8th), and in sixty days (17th October), the young 
made their escape. Thus, traces of vitality were manifest in 
each of the capsules about the same time as in those pre- 
viously mentioned ; that is, in three weeks : but, from this 
period to the exclusion of the young, five weeks had in the 
latter instance elapsed, whereas, in the former, this occurrence 
took place in the space of three weeks. This I can only 
account for, by stating, that the ova deposited on the 4th and 
14th of August were exposed to the sun, whilst those pro- 
duced on the 17th and 18th of the same month, were kept 
constantly in the shade. 
We shall now describe the manner in which these capsules 
are deposited. 
When the H. vulgaris is about to produce one of these 
bodies, it is observed to be greatly contracted both above 
and below the uterus. After having fixed its tail, which it 
does not once remove during the operation, it in the course 
of ten minutes presents the appearance represented in Fig. 3. 
At first, there is no difference as to colour between the dis- 
tended portion and the rest of the body ; but, in a few minutes, 
this part becomes of a milky- white colour, from the formation 
