90 SUPPLEMENT TO THE 



preserved; but in every case the final dip for a few seconds in the dilute acid is 

 indispensable. 



" In working out the smaller spirals, and in developing the connections of the spirals, 

 it is advisable sometimes to use the point of a small pen-knife instead of the larger knife 

 usually employed. It should be noticed, also, that in the case of small specimens the 

 spirals should be worked out from both sides of the shell so as to show transparently, 

 and that in most cases it is by transparency only that the connecting processes of the 

 spirals can be shown. Tlie transparency is greatly increased by wetting the specimens. 

 I have found nothing better than water for this purpose, though I have had many things 

 recommended. In the preparation of the smaller objects a hand lens nuist be constantly 

 used. The method above described will apply not only to the working out of the spirals 

 and their connections, but also to the working out of the loops of the Terebratulida^ &c. 



" Something must be said here about the use of sections, as some operators not only 

 use sections where they are indispensable, in the case of specimens with a hard limestone 

 matrix, bat also where they are entirely needless, in the case of specimens with a sparry 

 matrix. It has become the fashion with some, when they refer to their preparations of 

 the spiral-bearing Brachiopoda, to say that they have ' cut ' such and such a specimen. 

 Now, without regard to specimens with a sparry matrix, I object to the mode of operation 

 referred to, and this not only because it is altogether needless, but also, and much worse, 

 because the result of this cutting and making of sections is very often delusive. It must 

 not be forgotten that the publication of a single erroneous figure is an injury to science 

 and a stumbling-block in the path of further investigation. I would advise any one who 

 might desire to cultivate this field of research, to ' cut ' all such methods of arriving at 

 results, for their ease is only equalled by their uncertainty. 



" Since the first publication of the account of my process in the ' Carboniferous 

 Supplement,' I have found that it had been before observed that those specimens of the 

 Palaeozoic Brachiopoda which are filled with spar are peculiarly favorable for working out 

 the internal processes, and that the use of the knife and acid had been previously employed 

 for this purpose, though not, I think, exactly in the same manner as above described. 

 Mr. John Young, more than twelve years ago, operated with a knife and acid upon three 

 sparry specimens of AtJii/ris ambir/ua and one of Athyris Boysii, and more recently Mr. 

 James Neilson, jun., of Glasgow, has operated in the same manner upon specimens of 

 Athyris Boysii 2C(\^ Spirifera lineata. Herr H. Zugmayer, of Vienna, has also been lately 

 engaged in a similar work. The principal credit, however, is due to Mr. Whitfield, who, 

 for many years, has been engaged in developing the spirals and their connections, both in 

 siliceous specimens and in those which are filled with a sparry matrix. 



" As the result of my own careful and prolonged researches, I am convinced that 

 specimens with sparry interiors are more or less plentifully to be found of every species of 

 the spiral-bearing Brachiopoda. If, therefore, the method which I have described be 

 assiduously pursued in future investigations, there is nothing to prevent a satisfactory 



