279 



prevent shrinkage. In doing this it is only necessary to bring the water 

 in the test-tube to the boihng point and then let it cool. To make 

 microscope slides of the head parts it is not necessary to clear the head 

 in caustic potash or any other medium, as the various parts when dis- 

 sected are sufficiently transparent to permit of their thorough examina- 

 tion without clearing. Larval exuviae are of course the best objects 

 for microscope slides. To prepare these for mounting it is necessary 

 first to immerse them for twenty-four hours in 85 per cent, alcohol, 

 or for a shorter time in proof alcohol. After this a bath for about half 

 an hour in clove oil will be all that is required to fit them for mounting 

 in Canada balsam. 



It is a very difficult matter to make a satisfactory mount of a 

 pupa, containing the imago, and from the point of view of its availa- 

 bility for examination I prefer the cast skin. In mounting this the 

 same method is followed as with the larval exuviie. 



In making preparations of the imago for the microscope it is nec- 

 essary to clear the specimens in a ten per cent, solution of caustic pot- 

 ash. Large and heavily chitinized objects will require longer boiling 

 than small membranous ones, but no specific time can be given as that 

 necessary under any set of circumstances. It is only requisite that the 

 student observe the object from time to time by holding the test-tube 

 to the light and looking through it, judging when he has obtained the 

 desired transparency. It is best to use specimens which have been dry- 

 mounted. The hypopygia, which are used to a considerable extent in 

 descriptions in this paper, are easily mounted by the following method : 

 Boil in caustic potash as indicated above, wash in tepid water for five 

 minutes, dehydrate in proof alcohol for five minutes, and immerse in 

 clove oil for ten minutes for small objects, longer for large ones. 

 Have the Canada balsam rather thick, place a small portion on center 

 of slide, and on top of it a drop of xylol. Remove the object to be 

 mounted from the clove oil with a needle dipped in the balsam and ar- 

 range on slide under low power. This simple method will, I have 

 found, give highly satisfactory results. To prepare dry-mounted speci- 

 mens of the imagines for the collection it is best, except in the case of 

 very large examples, to mount them on their sides on card points, using 

 shellac, and keeping the upper surface of the thorax away from the 

 pin. By this method there is less danger of breaking the legs of the 

 specimens — a most important point to observe. 



SYNONYMY AFFECTING FAMII^Y NAMES 



The family name Chironomidcc and the subfamily names Ccratopo- 

 gonincc, Tanypincu, and Chironomina: are used in this paper, although 



