MONOGRAPH OF THE LABOULBENIACE^E. 



249 



to be possible, which I very much doubt, are not likely to afford data which could not 

 be as well or better observed by the examination of successive stages in individuals 

 naturally developed ; except, perhaps, in so far as concerns the possibilities of mon- 

 strous development which these plants might exhibit under such unnatural conditions. 



Preparation of Material for Examination. Having obtained a number of hosts 

 which are liable to be parasitized, it will found that from about five to fifty per cent, 

 will bear parasites. In order to obtain them for examination, the host should be 

 killed and impaled on a fine needle (a No. 12 sewing-needle mounted in a match is 

 the most convenient), care being taken that the surface of the insect remains perfectly 

 clean and dry, and then examined over a dull white, and then over a black surface 

 with a hand lens magnifying about eight or ten diameters, a dissecting microscope 

 being most conveniently used for this manipulation. Every portion of the insect 

 should be examined in different positions, and when the parasites have been dis- 

 covered, they should be removed by means of a dissecting needle like that just men- 

 tioned, the needle having been inserted in the match far enough to give it the 

 requisite stiffness, while its apex should have been ground on a fine oil-stone 

 until a sharp, slightly oblique chisel point has been obtained. With such a point, the 

 individuals are scraped off without much difficulty, and should be transferred to a very 

 small drop of water on the slide. When the desired number have been thus trans- 

 ferred, the individuals may be conveniently arranged by means of a fine hair mounted 

 like the needles. The excess of water should then be drawn away from the speci- 

 mens with a shred of blotting paper, and as soon as the moisture has dried around 

 them, they should be quickly treated with alcohol, and covered with a cover glass 

 which should always be supported by a shred of blotting paper or a chip of cover 

 glass. The alcohol should then be replaced by water, as quickly as possible, when 

 the individuals, will be found still living, if the manipulations have been sufficiently 

 rapid, and attached to the surface of the slide as a result of the slight drying just 

 mentioned. Although these directions may seem superfluous, it will be found that if 

 they are accurately followed, much trouble and the loss of many specimens will be 

 avoided. For permanent mounting, I have used only glycerine, to which is best added 

 a small amount of a saturated alcoholic solution of eosin, together with a trace of 

 common salt. This preparation is very satisfactory for general purposes, and should 

 be allowed to run under the cover glass and replace the water slowly, as it evaporates. 

 If the replacement is too rapid, the individuals will become shrunken, but generally 

 regain their normal form in a few days, or in a much shorter time. 



Dried material for herbarium specimens, which is always sufficiently good for 



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