Cleaning and Mounting Diatoms, etc. 211 



solution, washed in distilled water, and placed in absolute 

 alcohol for twelve hours ; then soak in absolute alcohol and 

 ether for a few hours, infiltrate, and embed in celloidin. 

 Cut sections in a microtome. Place sections in absolute 

 alcohol for about three minutes, clear in oil of origanum, 

 and mount in Canada balsam. 



If preferred, sections of sponges may be mounted in 

 glycerine jelly, but they must be soaked in water for a 

 little while before they can go into the jelly. 



2. The Skeleton (a) Horny Sponges. Boil in liq. 

 potassae, then wash the spicules well in water, and mount 

 in glycerine jelly or Canada balsam. 



(b) Calcareous. Dehydrate small forms in alcohol, clear 

 in clove-oil, and mount in Canada balsam in a cell ; or 

 separate the spicules by boiling in liq. potassae, wash in 

 water, and mount in Canada balsam or glycerine jelly. 



(c) Siliceous. Boil in nitric acid, wash well in water, 

 dehydrate, clear, and mount in Canada balsam. 



For the types in which siliceous spicules are embedded 

 in horny material, boil in liq. potassae for a few minutes 

 to disintegrate the tissues, then in nitric acid to clean 

 the spicules, wash well in water, and mount in Canada 

 balsam. 



Sections of Sponges. Harden in methylated spirit, 

 and transfer to equal parts of ether and absolute alcohol 

 for several hours. Then place in a thin solution of celloidin 

 for a day or two, transfer to a thicker solution of celloidin, 

 and soak again for a few hours. Eemove from the celloidin 

 on the point of a needle, and hold exposed to the air for a 

 few minutes to allow the celloidin to set around the speci- 

 men ; then push it off the needle into a bottle of methy- 

 lated spirit, and soak for a few hours to complete the 

 hardening. Embed in carrot, place in a well microtome, 

 and make the sections. Dehydrate in methylated spirit, 

 clear in oil of bergamot, and mount in Canada balsam. 



Sometimes sponge sections are rendered too transparent 

 by mounting in balsam. In such cases, mount in glycerine 



142 



