Anatomy of the Male Genital Tube in Coleoptera. 607 
the different groups, and even in allied species. In the 
Scarabaeidae it is nearly always excessively large, and is 
often produced into long diverticula (i. e. Hexodon, fig. 25a). 
In Lucanidae it is found in every stage, from a simple form, 
in which it is scarcely distinguishable from the stenazygos, 
to a form such as Lucanus cervus (fig. 8). In this species 
the internal sac is not drawn into the median lobe, but 
when at rest it is folded down on to the broad median 
lobe. The sac is produced into a long flagellum, supported 
on each side by a thin strip of chitin; the stenazygos* 
continues through the flagellum to its tip. To obtain a 
similar position of the orifice in Cerambycidae the great 
sac must be completely everted. 
The phenomenon of the internal sac being permanently 
everted is not confined to the Lucanidae, but appears 
among the Scarabeidae, Heteroceridae and Lycidae. In 
Spilota regina (fig. 20) the armature of the sac consists of 
two strong chitinous projections from the apex, and a strong 
chitinous plate beset with stout spines, the basal part of 
the sac being membranous. A comparison with allied 
forms demonstrates that these structures are part of the 
internal sac, and that the median lobe is normal in shape 
and size. In Metriorrhynchus (fig. 186) there is no doubt 
as to the everted condition of the internal sac, and it may 
be doubted whether its invagination is possible in some of 
these cases. 
The flagellum appears in various conditions, as to size, 
etc., in different families or portions of families. In the 
Brenthidae it reaches an enormous length and fineness, 
and at the base the stenazygos can be seen running into 
the flagellum, but further on they appear to amalgamate, 
as we cannot separate them. Among the Staphylinidae 
Pinophilus rectus has an enormous flagellum coiled up 
within the median lobe. The other forms of armature 
situated on the internal sac are very various, and have 
been described in many species in the special anatomical 
part of this memoir; cf. various species of Donacia (fig. 
199), and Carpophagus (fig. 204a). 
In another portion of this memoir we show that in many 
* In the special anatomical portion of this memoir we have 
always spoken of this stenazygotic portion of the tube as the “ejacu- 
latory duct,” but this is a functional term, and by other writers is 
often applied to the internal sac; it would probably be well to 
abandon it. 
SS 2 
