Anatomy of the Male Genital Tuhe in Coleoiitera. 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. 

 Zygos. Zygotic portion of the male genital tube ; and is 



formed by the two seminal ducts (a-b, 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 ditficult 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 



