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A Method of Separating Sponge Spicules by Filtration. 



By 

 L. R. Crawshay, M.A. 



The separation of sponge spicules by the method here described has 

 been employed by me from time to time, for some years past, with such 

 satisfactory results that it may be recommended with confidence as a 

 useful and time-saving method of preparing these or other minute hard 

 structures for microscopic examination. 



For the suggestion of gun cotton as a filtering medium I am indebted to 

 Mr. D. J. Matthews, the simple apparatus adopted for its use being as 

 follows : — 



A piece of glass tubing, about half an inch in inside diameter and eight 

 inches in length, is drawn out at one end rather abruptly to an opening 

 of about one-eighth of an inch or less, and this tube is passed through 

 a cork which serves to support it while resting loosely in the neck of a 

 flask or other waste receptacle. A very small piece of gun cotton, first 

 teased out evenly, is then pressed lightly with a glass rod into the lower 

 drawn-out end of the tube. This plug should be of the smallest possible 

 bulk sufficient to ensure easy filtration, and need not be more than about 

 one-eighth of an inch in depth. 



The spicules having first been cleaned in a test tube by boiling in 

 nitric acid or Eau de Javelle, and the test tube having been filled up 

 with distilled water in the ordinary manner, the contents are poured 

 into the tube and, the liquid passing through the filter, the tube is refilled 

 with distilled water and afterwards twice with 90 % alcohol. The 

 filter carrying the spicules is then pressed backwards into the tube and 

 shaken out through the broad end into a small test tube in which the 

 filter is thoroughly dissolved by shaking it up in equal parts of pure 

 ether and absolute alcohol, the tube being fitted with a cork to prevent 

 evaporation of the ether. When the spicules have settled the liquid is 

 pipetted off and the test tube is refilled with ether and alcohol and shaken 

 up as before. After pipetting of! for the second time the tube is then 

 filled with 90 % alcohol, from w^hich after being allowed to settle 

 again, the spicules may be removed for mounting on the slide. In this 

 way the gun cotton is removed in solution. If it is not, a deposit will be 

 left on the slide when the liquid is burnt oft' which will more often spoil 



