*9 
on the Hirudo vulgaris . 
without the capsule, using their utmost exertions to free 
themselves, but not being able to accomplish this, they have 
returned to their former situation, renewing their efforts occa- 
sionally, until their object was attained. 
At the time of birth, they are nearly colourless, and con» 
tinue so for many months, with very little increase as to size. 
They have the property of moving on the surface of the 
water, with their belly uppermost. I have noticed nothing of 
this nature in these animals, when fully grown. According 
to Muller, this faculty is possessed by the Hirudo hippoglossi ; 
he says, “ Praster hunc incessum (more geometrarum) alium 
in hac specie observavi, inversum nempe, dum corpore 
supino, summum aquae ore et cauda, alternating prehendit.” 
Hist. Verm. ii. p. 51. I have observed it to be also common 
to the Hirudo stagnalis and the Hirudo complanata. These 
animals, differing in several particulars from the leech, are 
now formed into a distinct genus ; to which, from their pos- 
sessing a retractile tubular tongue, we have given the name 
of Glossiphonia. 
Considering the quantity of the H. vulgaris that I pre- 
served, during the summer, I was surprised at the compa- 
ratively small number of capsules deposited. This was at 
length accounted for. Whilst watching one of them, during 
the formation of this membrane, I observed another move 
forward towards the same place, seize it in its mouth, and 
tear it into three or four shreds, which it left floating in the 
water. 
I now placed the H. vulgaris , singly, in different vessels, 
and found I could by this mode increase the number of the 
capsules. Each leech produced, in less than a month, from 
