J i la re as ts 
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CEREAL AND FORAGE INSECT INVESTIGATIONS. 
F, M. Wesster, In Charge. 
The use of the label ‘‘bred from” in bureau notes was discontinued some time ago and 
only ‘‘reared from” labels have been used. Mr. G. G. Ainslie in a letter to Prof. Webster 
brings up the question whether ‘‘bred from”? labels may not, after all, be of use with the especial 
significance that they apply only to material which has actually been ‘‘bred”’ in the sense of a 
breeder, that is the parent adults have been observed to copulate, the female to oviposit and 
the larva and pupa carried through to adult. This may apply also to the use of these terms in 
field notes. Discussion is invited.—L. O. H. 
THE CELLOIDIN METHOD. 
By Dr. Henry Fox. 
It frequently happens that persons engaged in histological or embryological investigations 
find the ordinary paraffin method of embedding and sectioning unsuited to the material being 
studied. In such cases the use of the method here outlined may yield satisfactory results. 
There are many modifications of the celloidin method, all of which are described in Lee’s 
Microtomist’s Vade-mecum, published by P. Blakiston’s Son & Co., 1012 Walnut Street, Phila- 
delphia. The particular method described here is that employed by ‘the majority of workers. 
It is known as the wet method. 
First, as to the advantages and disadvantages of the celloidin method as compared with 
the paraffin method it may be said that the only advantage found in the celloidin method is 
that it will frequently enable us to infiltrate objects which are either too large or too dense to 
be penetrated by paraffin and that the penetration of the celloidin can be effected without the 
use of heat. Paraffin on the other hand is suitable only for small and easily infiltrated objects, 
but where it is possible to use it, it should always be used for it is much more convenient and. 
gives much finer results than the celloidin method. The latter has the following disadvantages: 
(1) Objects must remain in the celloidin bath a long time to secure adequate infiltration, the 
time required varying from one to three weeks or even longer depending on the size and density 
of the object; (2) the sections must be cut wet which necessitates the use of a horizontal knife 
and consequently the possession of a sliding microtome; (8) the sections do not adhere so 
that serial sections are obtained only with difficulty and by the use of special methods of mount- 
ing; (4) very thin sections can not be cut, it being very unusual to get any sections less than 
0. 01 mm. in thickness and in the majority of cases it is necessary to cut them still thicker. 
It should be borne in mind that celloidin and the substances used to dissolve it are very 
- inflammable and should never be brought near a flame. 
The celloidin used at the Charlottesville station was obtained from the Arthur H. Thomas 
Co., of Philadelphia. It comes in tightly stoppered glass bottles containing one ounce of the 
substance. The celloidin is in the form of shreds immersed in water. 
To prepare solutions of the celloidin proceed as follows: 
Remove several shreds of celloidin from the stock bottle and, if they have been kept 
immersed in water, dry them as thoroughly as possible with filter paper. Then weigh out 
24 grams and return any excess to the stock bottle. Wash the weighed celloidin shreds in 
95 per cent alcohol for a few minutes, dry them on filter paper and allow them to remain 
exposed to the air in a warm place—say the top of the paraffin oven—for several hours. Take 
care to protect them from dust and do not under any circumstances bring them near a free 
flame. Allow the shreds to remain exposed to the air until they are thoroughly dry. 
