MOUTH-PARTS OF A COCKROACH 13 



transparent than before. After soaking in clean water for a 

 minute or two, transfer the pieces to a saucer of water 

 acidulated with hydrochloric, acetic or other acid, say one 

 per cent. Transfer again to clean water. The object of 

 this thorough washing is to remove the alkali, which is 

 apt to cling to the prepara- 

 tions. Then pass through 

 methylated alcohol and ab- 

 solute alcohol, using watch- 

 glasses or other vessels of 

 small size, for the sake of 

 economy. If many pieces 

 are placed in a small quan- 

 tity of absolute alcohol, the 

 liquid should be changed 

 once or even twice ; it is 

 necessary to remove the 

 water as completely as pos- 

 sible. Then transfer to a 

 saucer of turpentine. If 

 any appreciable quantity of 

 water is present, the pieces 

 will turn milky, and must 

 be replaced in absolute 

 alcohol. If they look clean 

 and bright, they are ready 

 for mounting. 



Take a clean micro- 

 scopic slip, and place a 

 small drop of balsam ex- 

 actly in the centre. It is 

 convenient to rule on a 

 card the outline of the slip, 

 and to draw diagonals, 

 whose intersection marks 

 the centre of the slip when 

 it is placed on the card exactly over the ruled outline. If any 

 bubbles appear in the balsam, break them with a hot needle. 

 Take out one of the preparations with a section-lifter, and 

 arrange it neatly on a glass cover. Lower the cover upon the 

 balsam with a needle, so that it gradually takes the horizontal 



Fig 12. — Maxilla of the first pair 

 (cockroach). Ca^ cardo ; .S"^, stipes; 

 La-y lacinia ; Ga^ galea ; Pa^ palp. 

 X 20. 



