242 PHYLUM ANNELIDA. 
parts, a twisted horseshoe-shaped glandular region, where 
the actual excretory function is discharged, and a spherical, 
internally ciliated bladder opening to the exterior. Within 
the latter there is a whitish fluid with waste crystals. 
Reproductive system.— The leech, like many other 
Invertebrates, is hermaphrodite, containing both male and 
female reproductive organs. The essential male organs or 
testes are diffuse, being represented by nine pairs, lying on 
each side of the nerve-cord in the middle region of the 
body. Each is a firm globular body, within which mother 
sperm cells divide into balls of sperms. The spermatozoa 
pass from each testis by a short canal leading into a wavy 
longitudinal vas deferens. This duct, followed towards 
the head, forms a coil (so-called seminal vesicle) as it 
approaches the ejaculatory organ or penis. From the coil 
on each side the sperms pass into a swollen sac at the base 
of the penis, where, by the viscid secretion of special 
(‘‘prostate”) glands, they are glued together into packets 
or spermatophores. These pass up the narrow canal of 
the muscular penis, and leave the body on the middle 
ventral line between rings 30 and 31, when they are 
transferred in copulation to the female duct of another 
leech. 
The female organs are more compact. The two small 
tubular and coiled ovaries are enclosed in spherical vesicles, 
the walls of which are continued as two oviducts, which 
unite together in a convoluted common duct. This is 
surrounded by a mass of glandular cells, which exude a 
glairy fluid into the duct. Finally, the duct leads into a 
relatively large muscular sac—the “ uterus”—which opens 
through a sphincter muscle on the middle ventral line 
between rings 35 and 36. 
The favourite breeding-time is in spring. Two leeches 
inseminate one another, uniting in reverse positions, so 
that the penis of each enters the uterus of the other. 
Spermatophores are passed from one to the other, and the 
contained sperms may remain for a‘ long time within the 
uterus, or, liberated from their packets, may work their way 
up the female duct, meeting the eggs at some point, or 
reaching them even in the ovaries. |The development is 
direct. 
