STRUCTURE OF NEPHRIDIA OF THE MEDICINAL LEECH. 291 
tively to the main curve of the horse-shoe in the living 
Leech. 
The vesicle duct, instead of passing into that limb of the 
gland which is the nearer to it, crosses the posterior limb 
externally, and joins the anterior limb. A portion of the 
gland, undescribed by previous observers, is found in the 
form of a delicate cord of gland-substance which extends as 
a free piece (a sort of third limb) from the centre of the 
concavity of the horse-shoe to about the middle of the 
posterior limb to which it is united. This is marked in the 
figure by the words Recurrent Duot.^’ 
It would not be difficult to give names to the different 
parts of the elongated horse-shoe shaped mass just described 
which might serve in further description did the minute 
structure of the gland in any way correspond with the super- 
ficial appearance. As a matter of fact it does not, and I 
have found it necessary to separate the following regions or 
lobes which have little correspondence with the general 
external form. 
The whole curve of the horse-shoe, from the point where 
the vesicle duct enters the anterior limb to the point where 
the recurrent duct joins the posterior limb, may be known as 
the MAIN LOBE. 
From the point where the recurrent duct joins the posterior 
limb to the point where the two prolonged and forwardly- 
bent limbs unite, including a portion of the anterior limb, 
is the APICAL LOBE. 
The outstanding process of the nephridium which comes 
into close relation with the testis, and which is given off 
from the anterior limb close to the enlarged commencement 
of the apical lobe, is the testis lobe. 
The little piece of the anterior limb extending from the 
base of the testis lobe to the commencement of the main 
lobe I shall leave for the present without a name, whilst the 
delicate piece depending from the main lobe and in which 
the recurrent duct commences may be called the recurrent 
piece ; ” it can hardly be called a lobe. 
IV. — The Ducts (Vesicle Duct, Central Duct, and 
Recurrent Duct). 
The divisions of the glandular portion of the nephridium, 
which we have just recognised, are necessitated by the dis- 
position of the duct and by the characters of the cells sur- 
rounding it. 
The duct in its various divisions appears as a cylindrical 
passage filled with a colourless liquid, and often contains 
