1 82 Appendix 



venient) and then transfer to absolute alcohol unmixed. 

 The ether must be got rid of before the next process ; 

 if any is left, a gas (ether vapour?) will appear in the 

 tissues and spoil the preparation, causing it to appear black 

 l)y transmitted light. From alcohol transfer to oil of 

 cloves to clear, then mount in an excavated cell with 

 balsam and benzine. New balsam should be used, or the 

 mixture should be newly boiled, so as to diminish the 

 risk of liberation of vapour. 



' Certain delicate structures, such as the branchial fila- 

 ments of the Sialis-larva, require special treatment. AVhen 

 the larva is immersed in the alcohol and ether mixture 

 add about lo per cent, of ether, and repeat this several 

 times until the mixture is almost pure ether. Transfer 

 quickl}'- to a second bottle containing enough pure ether 

 to cover the object entirely. To this add every day a few 

 drops of balsam mixed with benzine, and leave the cork 

 rather loose, so that the ether may slowly evaporate. 

 When nothing remains but balsam and benzine, the 

 preparation may be mounted. Onl}^ new balsam should 

 be used.' 



OTHER METHODS. 



For the examination of the minute structure of the 

 oesophageal valve sections were not found to be sufficient. 

 Much useful information was got from fresh preparations 

 treated with 2 j)er cent, caustic potash, and examined 

 while the alkali was acting. Teased-out preparations, 

 stained with haematoxylin or borax-carmine, and 

 mounted in glycerine, were also very useful. 



