AND ZOOGEOGRAPHY OF IXDIAN OLIGOCHiETA. 131 



matter, lighter in tint than that in the testis sac, in granules, 

 and also in larger spherical aggregations up to 20 /x in diameter. 

 The ampulla is attached by a connective-tissue mesentery to the 

 septum. 



The first part of the duct is wide— 125 /a — and has a consider- 

 able lumen ; it is lined by moderately high columnar epithelium, 

 with cilia which spring in bunches from each cell. The neck by 

 which it is joined to the ampulla is narrower, 60 /a in diameter 

 and similarly ciliated. The duct is also suspended by a mesentery. 



The coiled part of the duct is narrower, with a diameter of 

 50 /x ; it is remarkable for the great thickness of its muscular 

 coat — 15 1^1 — much more marked than in the previous portions of 

 the apparatus ; the fibres are mostly circular. The epithelium is 

 cubical and non-ciliated ; a lumen is not visible. The mesentery, 

 with marked muscular fibrils, branches to its attachment to the 

 various coils. 



The atrium in this species is small, and is contained within the 

 lower part of the septum ; it narrows downwards to pierce the 

 body- wall. The duct joins it near the apex ; but it is included 

 for some distance within a common connective and muscular coat 

 before the lumina coalesce. The epithelium of the atrium is high 

 and irregular, a,nd hence the lumen is small, and irregular also ; 

 the nuclei are situated towards the base of the cells ; there are no 

 cilia. The muscular coat is independent of the musculature of 

 the septum. In the body-wall the epithelium is lower, columnar, 

 non-ciliated ; the muscular coat is here apparently derived from 

 the circular fibres of the body-wall ; the diameter of the tube, 

 including its muscular coat, is 85 /x,. 



(7) Accessory {G ovulatory) Glands. 



The sexual animal is characterized by a number of markings, 

 each a transversely oval patch, slightly raised above the general 

 surface, with a circular groove in its centre ; these are two, three 

 or four in number, may be paired or unpaired, and may occur on 

 the ventral surface of segms. vii, viii, ix, and xii, or any of these. 



Corresponding to each of these markings there is found inter- 

 nally a small, almost spherical mass, attached to the body-wall by 

 a short stalk-like portion. On investigation by sections they pre- 

 sent the following characters (fig. 5): — 



Each is about "42 mm. in diameter, and is solid, its centre con- 

 sisting of a mass of cells. The outer thin coat of peritoneum is 

 in places perceptible only Avith difticulty; it appears as an ex- 

 tremely fine membrane with slight thickenings here and there 

 which represent much flattened nuclei ; in places it carries blood- 

 vessels. The muscular coat (m.) is very well marked — 9 /i thick ; 

 its fibres are derived from both the muscular layers of the body- 

 wall. There is no special (blue-staining) connective-tissue layer, 

 though there are traces of this tissue in between the muscular 

 fibres, as in the body-wall. 



The cells which fill up the interior of the organ (c.) are large, 



