224 THE SCOTTISH NATURALIST 



objects to mount successfully, but the following method 

 has given me excellent results : 



After catching, keep the larvae for a day or two in clean 

 water, that the alimentary canal may become emptied of its 

 contents. 



Pick the specimens out of the water and lay them on a cloth, 

 place beside them a piece of cotton wool soaked in chloro- 

 form, and cover the whole with a tumbler. The larvae will 

 die immediately. 



Transfer to 70 per cent, alcohol (not stronger, or the blood-gills 

 will burst) and leave for twenty-four hours. 



Substitute alcohol 75 per cent, and leave for twelve hours. 



Increase the strength of the alcohol by 5 per cent, every twelve 

 hours until the larva? are in 95 per cent. 



Increase to 97 or 98 per cent, and leave overnight. 1 

 . Substitute absolute alcohol and leave for twelve to twenty-four 

 hours. 



Replace by an equal mixture of alcohol and carbol-xylol. 



After an hour or two transfer to pure carbol-xylol for an hour. 



Make an equal mixture of carbol-xylol and clove oil, and 

 introduce this into the dish containing the lame, without 

 as yet drawing off the pure carbol-xylol. Wait for twenty-four 

 hours. 



Draw off this mixture and substitute a new supply of the 

 equal mixture of carbol-xylol and clove oil, and leave for 

 a day. 



Add a drop of clove oil at intervals for a day or two until 

 the mixture is more than 75 per cent, clove oil. 



Substitute pure clove oil, and leave for some hours. 



The specimen, with this care, should have gone through all 

 the changes without rupturing or losing its cylindrical 

 form, and may now be mounted in very dilute balsam in an 

 excavated slide. 



The critical points at which collapse is most likely to occur 

 are, 1st, in putting into absolute alcohol, and 2nd, in making 

 the exchange from carbol-xylol to clove oil. 



I use clove oil because the transference directly from 

 carbol-xylol to balsam caused serious collapse. The bath of 



1 Absolute alcohol itself is 98 per cent., but in practice we usually 

 regard it as practically water-free, and the above directions are given on 

 that assumption. 



