ON THE FOEMATION OF THE EGO IN THE ANNULOSA. 
613 
at each end contracts into a fine tubule {h), which Teevieafus traced a little way among 
the stomachal cseca and then lost. Tulk was scarcely more fortunate. He says of it, 
“ I examined the direction of these minute ducts ufith great care, and found that they 
pass forwards and curve round the tracheal trunks, near to their origin, from above 
downwards, and are lost at the inner extremity of the spiracular groove, where they 
may probably open externally. The function assigned to this part is thus rendered 
extremely problematical.” 
This description much excited my curiosity. A simple tube running transversely 
across the body, and opening at each side, would be an organ entirely without a parallel 
among the Articulata, or, so far as I know, in the whole animal kingdom. Moreover, 
after a little consideration I could not help thinking that this must be the testis, not 
only because it occurred only in the males, but also because its situation was much 
like that of the ovary, and because its contents much resembled immature sperma- 
tozoa. 
The contents of the abdomen are, however, so intricate, and the fine continuations of 
the tube are so closely attached in places to the trachese, and so delicate in themselves, 
that only after several failures did 1 succeed, in Ph. urnigermn and Leiohunus rotundus, 
in tracing what I may call the vasa deferentia of the testis beyond the tracheal trunks (c). 
At length, however, I succeeded in doing so, and found that they turned round again 
and passed with many convolutions to the central line of the body, where they fell into 
the delicate end of the common ductus ejaculatorius [d). Thus, therefore, all doubt as 
to the function of the Z-shaped tube is removed, and we see that the male and female 
organs of Phalanrjium offer the same parts, and are formed on exactly the same type. 
In both of them the secretory part, the testis in one sex and the ovary in the female, is 
in the form of a ring the posterior part of which is much wider than the anterior, while 
from the centre of the anterior half proceeds a tube which is rather short and very wide 
in the gravid female, while it is narrower and longer in the male. 
Mr. Newpoet, in his paper on lulus, expresses his admiration at the remarkable 
similarity existing between the generative organs of the two sexes in that genus. In 
this case, however, the simplicity is so great that the similarity is much less striking 
than in Phalanrjium, where both organs are of a most unusual form. 
The spermatozoa, as they are found in the ductus ejaculatorius, are minute spherical 
bodies, about -gT^th of an inch in diameter, of a greenish hue, and containing a brightly 
refractive, rod-like body. Whether, however, this is their definite shape I am unable to 
say, not having noticed them in the female. Leuckaet, in his justly celebrated article 
“Zeugung,” has given a nearly similar description of these bodies. Leydig^, how- 
ever, has obtained them from the vas deferens, and concludes, rather from noticing that 
they possess a tremulous motion than from any actual observation, that they are pro- 
vided with fine cilia. In P. imiigerum the accessory tubes were quite short, and much 
branched. 
* Loc. cit. p. 469. 
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