441 
The two worms A and B are opposed ventrally, the head of the 
one being directed towards the tail of the other. At least three means 
are employed in the union: 1) The clitelline setae (see below); 2) the 
secretion of the clitellum itself; 3) the capsulo-genous glands. These 
are matters of actual observation. It is probable, however, that other 
means may be occasionally used. For example, Dr. Hurst informs 
me that »a belt, apparently cuticular, arising from the papilliform en- 
largements placed ventro-laterally in segment XXVI [g in fig.], of 
each worm surrounds the body of the other.« 
The worms, being united (particularly by a strong band secreted 
by the clitellum), an exchange of seminal fluid takes place — that is to 
say, both worms discharge the contents of their seminal vesicles (see 
the dots and dashes in fig.). According to Vogt and Yung, the semen 
now streams down to the clitellum in furrows formed by longitudi- 
nal depressions of the integument, converted into ducts by the op- 
posing surface of the other worm. Having arrived at the clitellum, it 
passes into the spermathecae, the orifices of which are placed against 
the clitellum (the anterior end?). It is obvious that the discharge 
cannot be simultaneous, as the positions of the two sets of furrows 
would to a great extent be identical. But this is unimportant. Further 
the furrows, though clumsy, have this much to be said for them; viz. 
that, on account of the waste involved, their existence would explain 
the large development of the seminal vesicles, which certainly attain 
an inordinate size. Also, they would prove an interesting corollary to 
conclusions to be derived from a study of the genitalia of the earth- 
worm, inasmuch as their rough simplicity would be an excellent 
example of the temporary expedients adopted by nature in effecting 
»extensive morphological alterationsc. Nevertheless it seemed to me 
that their existence must be doubted, and was confirmed in this by 
what I observed recently. 
Whilst examining a very large number of worms, I came across 
two (both A. Zonga) which had external ducts connecting the orifices 
ofthe vasa deferentia in the 15th segment with the clitellum, and 
communicating with the tubercula pubertatis (see fig.). 
These ducts (which I shall call »seminal ducts«) seemed to consist 
merely of very narrow longitudinal inflations ofthe cuticle; but what- 
ever their precise nature, there could not be the slightest doubt of 
their presence, for they were to be clearly seen in the living animal. 
On cutting sections, however, I was disappointed to find only doubtful 
traces of the canals, and they certainly contained no sperms, although 
I stained some sections for them. If, as I suppose, the seminal ducts 
are only fragile evaginations of the cuticle, it is easy to explain how, 
