SEXUAL PHASE TN INDIAN NATDID.T;. 



465 



is soiiiewliat lieart-sliaped, or o\ oid and notched Ijeiow wliere the 

 duct arises. Its size varies somewliat : in height it may be from 

 '207 t<) 270 /Lf, its length antero-posteriorly rather greater and its 

 width rather less. The ampnlhie are filled with spermatozoa, and 

 are so large as nearly to fill up the wl)ole segment, the remaining 

 organs occupying only a small space below tlieir contiguous inner 

 walls. The part of the ampulla anterior to the duct is somewhat 

 bulged downwards, and is lined with columnar cells ; the part of 

 the wall behind the duct is lined with cubical cells, which 

 gradually decrease in heiglit as they pass upwards on the posterior 

 wall ; the rest of the ampulla is lined by a very thin epithelium 

 of attenuated cells whose outline is quite indistinct. Outside 

 the epithelium there is a thin coat of circular muscular fibres — 

 the only part of the wall visible o\er a, large portion, on account 

 of the thinness of the epithelium. The spermathecal duct leaves 

 the ampulla below, nearer its anterior wall, and is about 130-140 fx 

 in height, including the depression of the body-wall where it 

 opens to the exterior. The duct is narrow above and below, but 

 somewhat swollen in the middle ; its epithelium consists of 

 narrow columnar cells having elongated nuclei. There is a thick 

 covering of muscle-fibres outside the epithelium. The sper- 

 mathecal opening lies internal to and at the level of the ventral 

 setfip of the fifth segment, some distance behind septum 4/5. 



The penial set?e are the modified venti-al, seta) of segment vi. 

 They are two or three in a bundle, somewhat hooked at the 

 distal end, which is not bifid. In length they are about 132 ^ ; 

 the shaft consists of a distal narrow portion about 36 ^ long, and 

 a proximal stouter part 96 /j long ; there is no distinct nodulus, 

 l)ut the distal narrow portion is bent outwards and thus not in a 

 straight line with the proximal segment (text-fig. 1). 



References to Literature. 



1. Beddard, F. E. — "A New Bmuchmte OUgochsete (Branchim-a 



sowerhyi)y Quart. Journ. Micr. Sci. vol. xxxiii., 1892. 



2. Stephenson, J. — "On Branchiiira soverhyi Beddard, and on 



a new Species of Lliniioclrilus with distinctive characters." 

 Trans. Eoy. Soc. Edin. vol. xlviii. pt. 2, 1912. 



3. Stephenson, J. — '-On the Sexual Phase in certain of the 



Naidid^e." Ibid. vol. li. pt. 4, 1915. 



4. Stephenson, J. — "On Hamionais Icmrentii, sp. n., a represent- 



ative of a little-known Genus of Naididse." Ibid. vol. li. 

 pt. 4, 1915. 



