PLANARIANS FROM MAURITIUS AND RODRIGUES 149 
oblique upwardly directed, annular outbulging, and which 
receives the penis-sheath from above. The vestibulum has 
a wall consisting of a single epithelium and a muscular layer, 
while the penis-sheath is lined with a cihated epithelium, 
outside which is a thick muscular coating, chiefly composed of 
circular fibres. 
Male Organs.—The numerous testes, containing sperma- 
tozoa in several stages of development, are arranged in a row on 
each side of the body close to the upper side of the longitudinal 
nerve cords, extending from behind the ovary to the insertion 
of the pharynx. The vasa deferentia run backwards, just along 
the inside of the nerve cords. Shortly in front of the penis they 
eradually bend inwards and upwards, finally to open as a rule 
separately into a moderately wide seminal vesicle. The vas 
deferens shows a definite wall consisting of a thin epithelium 
and a feeble muscular layer of circular fibres. 
The penis is a conical body, hanging from above subvertically 
in the pear-shaped penis-sheath, and encloses a cavity, the 
seminal vesicle, which gives rise to the ejaculatory duct, opening 
into the sheath at the tip of the penis. The vesicle is coated 
internally with a thick glandular epithelium, which projects 
into the lumen of the organ in folds. Embedded in the body- 
parenchyma around the penis-bulb are numerous glands, the 
ducts of which enter the penis at the base and open into the 
penis-sheath over the surface of it. 
Female Organs .—lI am unable to give an account of the 
ovary, as I have been reluctant to sacrifice the anterior half of 
the body to the microtome. Probably the paired ovary occurs 
in the usual manner. The vitelline glands, which are composed 
of large cells closely packed, extensively fill up the interstices 
between the gut diverticulae. They are in connexion with the 
oviduct at numerous points by means of a short cylindrical 
duct. 
The oviducts lie close to the dorso-lateral side of the nerve 
cords, one on each side, in which position they proceed straight 
backwards, receiving the contents of many vitelline glands. 
Behind the genital opening they near the median line, shghtly 
