15. METHODS OF INVESTIGATION 147 



can be made with dividers or an eyepiece micrometer. The adhesive plaques 

 and the toothed bristles of the girdles can most conveniently be studied on 

 unstained whole mounts in glycerine jelly. In order to study the spermato- 

 phores, whose size and shape are important systematic pointers, they should 

 be removed from the anterior part of the spermduct of the male, then, after 

 staining with haemalum, mounted in glycerine jelly or Canada balsam. [I 

 would recommend phase or "Anoptral" contrast for spermatophores — E.C.S. 

 The polarizing and interference microscopes are also useful — D.B.C.] 



Study of the internal anatomy and histology of Pogonophora is only 

 possible in sections; whole mounts show very little. Small species may be 

 embedded in paraffin wax and sectioned while still in the tube (e.g. Sibo- 

 glinum caulleryi, S. ekmani, etc.). To obtain good sections it is no doubt far 

 better to use proper histological fixatives, but on many occasions alcohol has 

 given quite good results. Sections may be stained differentially with borax 

 carmine, iron haematoxylin, Mayer's haemalum, Mallory's triple stain or 

 azocarmine. [I have found it difficult to section material which is still in the 

 tube without softening the tube first by some means. Diaphanol has the usual 

 drawbacks of grossly damaging the tissues and is not really suitable for 

 anything except whole mounts. I have been successful in using enzymic 

 digestion of the chitin of the tube (Carlisle, 1960) — D.B.C.] 



