PLANARIANS FROM MAURITIUS AND RODRIGUES 145 
lined by a thin, flattened epithelium of nucleated cells resting 
upon a basement membrane. 
The penis consists of two parts, viz. the free, conical intro- 
mittent part lyimg subvertically in the penis-sheath, and the 
bulbous basal part of muscular nature. Hnclosed in the latter 
part is a wide cavity of somewhat irregular contour, the seminal 
vesicle, into the anterior extremity of which open the vasa 
deferentia ; posteriorly this is continuous with the ejaculatory 
duct which opens into the penis-sheath at the tip of the penis. 
The cavity is lined by a layer of columnar glandular cells, 
beneath which is a circular muscular layer. Embedded in the 
parenchyma of the penis are numerous glands which open into 
the seminal vesicle and the ejaculatory duct. Externally the 
penis is covered with a thin epithelium which becomes thicker 
towards the proximal portion, and at the same time is provided 
with cilia. The epithelium surrounds a muscular layer 
consisting of external, thick, circular, and internal, thin, 
longitudinal fibres. On some occasions the penis at the proximal 
parts gives rise to special processes which are covered with an 
epithelium made up of ciliated, columnar cells. 
Female Organs.—tThe paired ovary is situated far behind 
the brain, one on either side close to the dorso-lateral side of 
the longitudinal nerve cord. Each ovary is nearly oval in 
shape, and its cavity is lined with a thin epithelium, composed 
apparently of a single layer of flattened cells. In the interior of 
the ovary, ova in various stages of development are met with. 
Occupying the periphery of the ovary occur numerous young 
ova, each with an oval, large, and highly granular nucleus. In 
the successive stages of development the ovum assumes a nearly 
spindle-like shape, as has been mentioned by Dendy. The large 
nucleus sometimes shows a very distinct chromatin network. 
Situated in the central and lower regions of the ovary are the 
ripe ova, which present a round shape and enclose a very large 
nucleus, revealing a transparent, vesicular aspect. 
The vitelline glands are represented by irregularly ramified 
masses of cells, which are extensively distributed in the inter- 
stices between the diverticulae of the intestinal trunk and stand 
NO. 257 L 
