164 W. B. BENHAM. 



Beddard has shown, is not a primary but a secondary condition. 

 As regards the sperm-duct, I would suggest that we have in 

 Sparganophilus an explanation of the long duct so usual 

 amongst earthworms ; the sperm-duct probably opened exter- 

 nally in the segment following the funnel Just as the oviduct does 

 in all earthworms, and the sperm-duct in Moniligaster, and 

 many of the aquatic Oligochaeta, such as Naididse, Tubificidse, 

 &c. In order to convey the spermatozoa backwards a groove 

 might be imagined to appear, which sinking into the epidermis 

 became a canal. This canal lying, as in Sparganophilus, 

 within the epidermis, would extend through any number of 

 segments till it opened to the exterior. Accessory parts, such 

 as atria, would appear later on; the duct sank deeper and 

 deeper till it came to lie in the coelom, as in the majority of 

 worms. I do not wish to be understood as regarding Spar- 

 ganophilus as a primitive form, but merely suggest that in 

 this particular feature it retains an archaic character. 



The position of the duct is shown in fig. 19, where it is seen 

 lying amongst the bases of the deep clitellar cells, dorsad of the 

 ventral chsetse, and immediately outside the tubercula puber- 

 tatis. In fig. 20 the structure of the sperm-duct is seen to be 

 normal ; the worm, of which this figure represents a portion of 

 a transverse section, had passed its sexual maturity. The 

 ordinary clitellar cells (see fig. 30) appear to have undergone 

 a certain amount of change, the contents have been poured 

 out in forming the cocoon, and an appearance as of a '' cutis" 

 is presented by the nuclei scattered iu a loose network of fibrils, 

 the shrunken walls of the cells. 



In Somite xviii the duct becomes more superficial (fig. 21) 

 where it lies immediately below the ordinary epidermal cells. 

 At the hinder margin of this somite it reaches the surface, as 

 seen in fig. 22. The male pore is very minute, and there are 

 no accessory organs to call attention to its whereabouts, and 

 it may be very readily overlooked ; in the section drawn the 

 terminal portion, for some half a millimetre in extent, was 

 filled with deeply stained spermatozoa — evidently I captured tiie 

 worm at its )nost active period — which mark the duct distinctly. 



