858 General Notes. 
2. To specimens which have been already hardened and preserved 
the solvent may also be applied; but in all cases where fresh mate- 
rial is easily obtainable, it should immediately have its chitin soft- 
ened and then afterwards be preserved. Here the method is some- 
what shorter, since the substance has been previously hardened. 
From alcohol—weak solution—they are put into the Labarraque 
and softened as above, then passed through water and the alcohols, 
ete. 
In most cases in which an animal. egg or embryo is encased in 
chitin, the best results have been obtained by staining the sections 
after they have been cut and fixed to the slide. If the specimen is 
small, staining in toto—after having the chitin softened, or if before 
this has taken place, after having made an entrance through the 
chitin with a point of a needle—is equally good. The greatest 
difficulty, and practically the only one which one meets with, is 
that the Labarraque solution not only attacks the chitin itself, but 
after a time the soft tissues of the animal—apparently the connect- 
ive tissue. Where the chitin surrounds the object completely, as 
in the case with the roach’s raft, one can remove the object from 
the solution as soon as the chitin is softened, and before the under- 
lying parts have been attacked. In cases like this the solvent is at 
its best 
Very often, however, the soft tissues of the animal are ex 
in places between the chitin covering. This is well illustrated by 
the joints of insects’ legs, etc., and very frequently these expo! 
places are attacked before the chitin is completely softened, thus 
causing the joints, if much handled, to fall apart. 
By judiciously diluting the solution and taking the parts to be 
softened from it before the joints are attacked, one will find its 
application practicable even here. 
The greatest difficulty of all is when the chitin is internal, com- 
pletely surrounded by soft tissue. So far as I have made any 
experiments here, I find that one gets better results with very 
dilute solutions—diluted from eight to ten times, or even more. 
It m admitted that in this last case the application of the 
solvent is more doubtful, and of not nearly so much service as 10 
the first and second supp cases. ‘a 
Strong solutions, then, had better be used only when the chitin 
completely surrounds the soft animal parts, and dilute solutions 
must be used in all cases where these latter substances are expose 
The solution not only softens the chitin, but removes all pig! 
either in the chitin or in the tissue beneath, and this is at ames 
advantageous. 
THe Use or CELLOIDIN IN MAKING DEMONSTRATION-PREPA~ 
