Parker. — On preserving Cartilaginous Skeletons. 261 



therefore not a great success ; Raja was prepared without previous immer- 

 sion in alcohol, and although a vast improvement on the ordinary skeletons 

 of the same fish, is not so good as one could wish; but Cestracion and Trygon 

 show, up to the present time, remarkably little alteration, the latter having 

 been removed from glycerine jelly for about six weeks, the former for fully 

 three months. 



The success of the method is most marked in purely cartilaginous 

 parts, such as the branchial arches, with their delicate branchial rays, 

 which after many months retain their flexibility and translucence unim- 

 paired. The thicker parts of the skeleton show, naturally, the greatest 

 amount of distortion, and this is particularly marked when there is a 

 thickish superficial layer of calcific matter, as in the jaws, etc., of Elasmo- 

 branchs: with these parts, the shrinking of the cartilage always produces a 

 slight cracking of the bony matter, but as a similar though less marked 

 cracking is seen in spirit specimens, I do not see how it is to be altogether 

 obviated, unless, perhaps, by using a larger proportion of glycerine. 



It is always advisable to allow the specimens several weeks to dry ; when 

 the surface no longer feels sticky they are varnished with a solution of 

 white shellac in rectified spirit, the operation being conducted in a warm 

 dry room, as the slightest damp produces precipitation of the shellac. If 

 properly managed, two or three applications of this varnish produce a dry 

 and smooth but not too glossy surface. * 



In mounting skeletons prepared in this way, the best plan is to make a 

 framework of japanned wire, of such a form as to serve as a series of rests, or 

 "cradles," for the several parts ; the gills are best supported on a special light 

 wire framework. Unless absolutely necessary, no attempt should be made 

 to fasten parts together with wire as in ordinary articulating, and when this 

 has to be done, neither iron, copper, nor brass wire is admissible ; silver or 

 platinum only should be used if " glycerine jelly A " has been employed, 

 with "B," pure tin would probably be safe. The method of mounting 

 recommended has the advantage of allowing each part to be separately 

 removed for examination ; this of course adds greatly to the value of the 

 skeleton for teaching purposes. 



2. Partly ossified skeletons. Of these I have had prepared skeletons of 

 Ceratodus, and of foetal calf and foal, and two skulls of the trout, and hope 

 before long to get examples of the various genera of Ganoids and Urodela ; 

 the method has also been employed with good results for the mesethmoid 



* Some recent experiments seem to show that a better varnish is afforded by a solution 

 of dried Canada balsam in benzol, or by equal parts of undried Canada balsam and 

 solution of gum benzoin in methylated sphit. 



