Anatomy of the Male Genital Tube in Coleoptera. 483 
basal-piece together. It is the ring (Hopkins), Gabel 
(Lindemann). 
VENTRAL PLATE (vp, fig. 19, etc.). A sclerite on the 
anterior ventral surface of the basal-piece in some 
Lamellicorns. In some cases the lateral lobes are 
consolidated to its anterior edge. The chitinisation 
of this part varies much. 
Zycos. Zygotic portion of the male genital tube; and is 
formed by the two seminal ducts (a—0, fig. 239) 
proceeding from the testes. 
METHOD EMPLOYED. 
In preparing this memoir it was necessary to make use 
of a great deal of dried material, some of it fifty and 
sixty years old, as our time was limited and we could not 
procure fresher specimens. In such cases we found the 
following methods acted very well and, if care was used, 
did not destroy the specimen. The dried specimens were 
placed in water and allowed to soak for a time according 
to the size and condition of the specimen, the water being 
heated if necessary ; when thoroughly relaxed the aedeagus 
was dissected out, either through the opening between 
the last dorsal and ventral plates, or the last segment was 
taken off, or the abdomen was taken off at the base, the 
aedeagus extracted through the basal foramen and, when 
necessary, the abdomen stuck on to the thorax again. The 
aedeagus was then placed in weak caustic potash for a 
time when the muscles would swell up and could then be 
dissected ; in cases where it was necessary to clear off all 
the muscles the caustic potash was used very strong. To 
get the internal sac evaginated was a more difficult. matter ; 
but with care it was possible to do this by the use of 
localised pressure, and with the aid of a very finely pointed 
syringe. By inserting the fine point into the median 
foramen and gently applying pressure the internal sac can 
be forced out in a manner, if not quite natural at least 
near enough to study its shape and structure. 
With fresh material it was a much easier matter, espe- 
cially with bulbous forms such as are found among the 
Staphylinidae; by placing the aedeagus in water and 
gently pressing upon the bulb the internal sac can be 
made to evaginate in a perfectly natural manner. 
To study»the position taken up by the internal sac 
