338 NATURAL HISTORY OP 



tained. An attractive way of arranging a collection 

 of Lepralice, and otlier similar species, the structure of 

 which is entirely invisible without microscopic obser- 

 vation, is to mount the shell which bears the incrusta- 

 tions on a piece of cardboard, and to annex below it 

 on the same piece a drawing of the cells enlarged to a 

 known scale; the card bearing the zoophyte and drawing 

 should then be placed in a glass-topped box. This 

 enables friends or others interested to appreciate a 

 collection better than the exhibition of a lot of ap- 

 parently similarly incrusted shells or stones. A speci- 

 men of every species obtained should be mounted as a 

 microscopic slide. Those which will show well as 

 transparent objects should be cleaned in spirits of 

 wine, afterwards passed through oil of cloves, then 

 into benzole, and lastly mounted in balsam let down 

 with benzole. Some of the hydroida show their struc- 

 ture most satisfactorily when stained ; picrocarmine and 

 haematoxylin are the best media to use for this purpose. 

 If the specimen is obtained alive, and it is desired to 

 mount it with the polyps exserted and their tentacles ex- 

 panded, the best method for killing them so as to show 

 these features is to select a portion of the zoophyte, the 

 polyps of which are healthy and active, and place it in 

 a watch-glass or glass beaker, according to size. After 

 letting the specimen alone for a short time, seize an 

 opportunity when the polyps are extended, and with a 

 pipette or dipping-tube drawn to a fine point, let a 

 drop or two of absolute alcohol run into the water 

 down the glass so as not to fall directly on the polyps. 

 The repetition of this once or twice seems to stupify 

 the zoophyte, and after the lapse of an hour, if the 

 polyps be still extended, alcohol may be added slowly 



