INTRODUCTION. 13 
shrinkage will cause it to cockle. The shell may be placed beside 
the skin and the name and locality written on the card. When the 
skin is thoroughly dry it should be varnished with colourless varnish, 
which will bring out and preserve the markings. The small species 
will be found more difficult to deal with. 
Darts. 
There is a curious internal organ connected with the reproductive 
system of about two-thirds of our British HeZzces and also of Hyalinza 
netida and H. excavata which deserves attention. These ‘‘darts” are 
not only exquisitely beautiful objects in themselves, but they have a 
specific value which is particularly useful in distinguishing He/ex hov- 
tensis from H/. nemoralis. These little objects under the lens resemble 
curiously flanged spear-heads. They are enclosed in a pouch, the 
‘* dart sac,” from which they are best separated by dissolving away 
the ‘‘ sac ” in a solution of caustic potash. They show well mounted 
on black card. For a full account of this organ I must refer those in- 
terested to a series of papers and illustrations in the ‘‘ Journal of 
Conchology,” vol. iv., by the late Mr. C. Ashford, of Christchurch 
(Hants. ). 
THE ARRANGEMENT OF A COLLECTION. 
Much of the pleasure derived from a collection consists in its 
arrangement. A cabinet with drawers is undoubtedly the best recep- 
tacle, but a series of flat boxes will answer the purpose very well. 
Various methods of setting out the specimens are adopted. Some 
prefer slabs of wood or glass covered with stone-coloured paper, on 
which the shells are fastened with gum. This is doubtless an excellent 
plan for showing off the shells, especially in a museum or a perfect 
collection where the shells are not supposed to be touched; but in the 
-case of a collection which is constantly receiving better specimens to 
be substituted for those already stuck down, this method has an 
obvious drawback. There is no doubt that specimens are best shown 
and protected by glass-topped boxes. These are made rectangular 
