The adult organisation of Paragordius varius. 455 
slit (Cl. Ap Figs. 81, 82, Pl. 42), sometimes nearly closed, sometimes 
widely open. No chitinous spiculum was observed in any individual 
in the cloaca, but in two a rod-like glandular mass, evidently a 
secretion from the vasa deferentia. It is probably this secretion, 
together with that from the anterior portion of the testes, which forms 
the mucous envelope (Sp.Secr Fig. 68, Pl. 41) around the mass of 
spermatozoa (Sp) when in the receptaculum of the female. There is 
no special cloacal muscular diaphragm such as occurs in Gordius. 
The innervation of the cloaca is close to its external opening, where 
nerve fibres enter its epithelium from the contiguous neural lamellae 
of the caudal nerves (Fig. 86, Pl. 43). The genital nerves (Gen. N 
Fig. 89) as previously described, pass from the dorso-lateral angles 
of the anterior end of the cloacal ganglion (Cl.G) into the fibrous 
sheath (Vas. $) around the vasa deferentia (Vas). 
The mature spermatozoon (Fig. 91, Pl. 43), as found in the re- 
ceptaculum seminis of the female, appears to be very simple in 
structure, showing a rod-shaped chromatic head and a long, cytoplasmic 
flagellum; sometimes the latter appears segmented, but this is probably 
a dissolution phenomenon; neither acrosome nor middle piece could 
be distinguished. In an immature male from the body cavity of an 
Acheta, and with thin white cuticle, the testes were relatively much 
larger than in the free stage of the worm, and filled with what were 
evidently spermatocytes in the prophase (spirem) of the first matu- 
ration division; but the preservation of them was too poor to allow 
a careful study. In the receptaculum seminis of the female the 
spermatozoa are enveloped by a thick mucous sheath (Sp. Seer Fig. 68, 
Pl. 41), which we have seen is probably a secretion of the male; this 
might indicate the formation of a large spermatophore, as has been 
described by VILLOT. 
Literature on male genital organs. VıLLor (1874, 1887, 
1889c) describes two “tubes testicolaires”, each with an inner epithelial 
lining. He considers the “bursa copulatrix” of VEJDovVvskY (1886) 
as simply a coagulated mass of spermatozo® (as does von LinsTow, 
and as I also would interpret it). VespovskŸ (1886, 1894) describes 
these tubes as “Samensäcke”, and considers that only the anterior 
end of them should be regarded as “testes”, since only here did be 
find cell formation. von Linstow (1889), on the other hand, finds 
that in the immature stage the whole wall of the “Hoden” proliferates 
Zool. Jahrb. XVIII. Abth. f. Morph. 30 
