BY THOS. STEEL. 117 



shrinking too much as the spirit hardens it. A few minute-; 

 suffices for this, and it is now left while the others are being 

 similarly treated. When all are finished they are transfei-r,' I, 

 with strong spirit, to the tubes or bottles in which they are to o^ 

 preserved. 



The great drawback to the use of spirit in preserving those 

 worms is the solubility of the colouring matter of many of thcin 

 in that menstruum. 



The beautiful yellow and green tints are completely removed, 

 leaving the previously elegantly coloured parts bleached and 

 white, the spirit meantime becoming yellow. 



Fortunately the colours soluble in spirit are usually confincn] 

 to the areas of body colour; the characteristic bands, lines, i*-c , 

 being of a dark pigment which is but slightly affected thereby. 

 I hav3 made numerous experiments with the view to preserve 

 land planarians in their natural colours. It is necessary to use 

 some medium which, while capable of preserving the animals, does 

 not dissolve or destroy the colour. I have tried a large number 

 of substances, such as different strengths of Formaline, alone and 

 combined with spirit, various saline solutions, etc., and though I 

 have failed to discover a medium entirely to my satisfaction, it is 

 perhaps as well to record such amount of success as I have had. 

 The preservative which I have found to answer best of all is 

 chloroform. So far as preserving the colours is concerned it ans^\ rrs 

 perfectly, but its high specific gravity — causing specimens to float 

 — md its volatility, are somewhat serious objections. Common 

 kerosene is another medium which, while not so efficient as 

 chloroform, gives a very good retention of colour. 



Before putting into either chloroform or kerosene, it is neces- 

 .sary to harden the specimen a little in strong spirit, the action 

 of this being to displace water from the tissues. 



The worms are killed and cleaned as already described and 

 then put in strong spirit until the colour is seen to just begin 

 tinging the spirit. Each specimen is laid for a moment on a 

 piece of blotting paper to remove surplus spirit, and then put 

 direct into the chloroform or kerosene. 



