23 
1907 - 8 .] Oligochaets found on the Scottish Loch Survey. 
There are two pairs of testes, the anterior in IX, the posterior in X. On 
each side there are two vasa deferentia, the anterior piercing the septum 
9/10 and running back to the glandular atrium in segment X, while the 
posterior opens by a funnel into segment X, and running back through the 
septum 10/11, turns on itself, and again piercing septum 10/11, runs 
forward to the atrium. 
There is a single pair of ovaries in segment XI, and a short oviduct 
which pierces the septum 11/12 to open to the exterior in the anterior region 
of segment XII. 
The Male Genital Apparatus . 
The testes are four in number, the anterior lying in segment IX on 
either side of the nerve cord (Pl. I. fig. 1), the posterior lying in a correspond- 
ing position directly upon the anterior vasa deferentia in segment X. (fig. 
3). The greater part of the maturation of the sperm appears to take place 
in the seminal vesicles, which are very large. These consist of paired sacs, 
the anterior of which lie in segment VIII and the posterior in segments 
X, XI, XII, XIII. 
The vasa deferentia open by large funnels into their appropriate seg- 
ments, slightly dorsal to the gut. There is a slight difference as regards 
the aperture, which in the anterior opens directly into the seminal vesicles, 
whilst the posterior open into the body cavity. 
The atria are rounded glandular structures, composed of the following 
layers from within outwards, — 
(1) a single layer of large cells with flattened basal nuclei and a clear 
periphery ; 
(2) a layer of circular fibres ; 
(3) an irregular mass of clear cells, with large nuclei and granular 
contents. 
The atria opens directly into the penes, which are long tubes directed 
backwards, and about equal in length to the transverse diameter of the 
worm. 
The Female Generative Apparatus . 
The ovaries lie in the anterior part of segment XI. 
Yejdovsky and Beddard distinguish three main types of egg formation 
in oligochsets, and they agree in placing the Lumbriculidse amongst those 
forms in which—- 
(a) any cell in the ovary may become an ovum, and 
( b ) no share is taken in its development by the surrounding cells. 
