MORPHOLOGY OF MELIBE 569 



spermatotheca. It is possible that the secretion serves to 

 form small pockets of spermatozoa or spermatophores.' 



MacFarland (1912) fomid, in the Dironidae, that the 

 spermatotheca was almost rudimentary, and that the dilated 

 oviduct seemed to have assumed in part the function of a sperma- 

 totheca, ' for it is frequently crowded with spermatozoa, while 

 the spermatotheca itself contains relatively few.' On the 

 contrary, 'in D i r o n a 1 b o b i n e a t a the oviduct is short 

 and slender : spermatotheca very large, reaching a diameter 

 of 1-3 mm., total length being 4 mm. in a large specimen'. 

 In this connexion it is well to note that, in M. leonina, 

 which has a large spermatotheca, the male germinal product 

 also frequently passes into the distal regions of the female 

 genital duct system even as far as and including the prostata. 



(5) The Male Genital Duct. 

 The male genital duct starts in the hermaphrodite gland as 

 small tubules (PI. 37, fig. 81, Ve), which join into a common 

 median duct that enlarges into a round bulb-like part {Amp) at 

 the anterior region of the ovitestes (gonads). This enlargement 

 I have called ampulla. From the ampulla the male duct passes 

 anteriorly as a large organ of fibrous tissue (PI. 28, fig. 9, Vd). 

 It is surrounded by a sheath of its own (PI. 37, figs. 78, Iglj), 

 74, 76, 77, 79, 83, Oc). Intervening between the penal sheath 

 and the penis itself, is lymph or mucus, a colourless, structure- 

 less substance (M). The penis is covered with cells of epithelial 

 structure, perhaps both of these, and the cells of the lining of 

 the penal chamber just described, secrete the mucous substance 

 also mentioned. The organ itself is made up mainly of fibrous 

 connective tissue (PI. 37, figs. 75, 78, 83, Int, Ml). In fig. 75 

 the biluminate effect as shown here is due to the coiled condi- 

 tion of the organ at the point of section. The main bulk of the 

 organ consists of this fibrous tissue (PI. 37, fig. 76, P). The 

 lumen of the organ is lined with ciliated cuboidal epithelium 

 (PI. 37, fig. 83, lepl, cil). The ampulla of the penis seems to be 

 quadroluminate ; anteriorly these lumina converge into three, 

 then tw^o, and finally into one, wdiich becomes the seminal tube 



