202 M. M. Mercaur 
the species at my disposal execpt O. zellerz. The results will be 
given in the proper connections. They are also shown in a table 
in the appendix. 
For fixing I used chiefly Scuaupinn’s alcoholic-corosive-sublimate, 
corosive-sublimate-acetic acid, picro-acetic acid, Friemmrne’s fluid, 
formol, and absolute alcohol. Of these corosive-sublimate-acetic acid 
(20 minutes to 36 hours) gave the best results and in the later work 
was chiefly used. 
For staining im toto I used principally GRENACHER’s borax 
carmine, Maypr’s paracarmine, Mayer’s haemalum, and DELAFIELD’s 
haematoxylin. Paracarmine did not give very good results. Borax 
carmine gives a good general stain, but does not show the finest 
details with sufficient clearness. If a thin sheet of green gelatine 
be placed on the table of the microscope beneath the slide, the 
definition of detail is much improved,') but even then the borax 
carmine preparations are not the best. No satisfactory stains were 
obtained with Mayrr’s haemalum, except for protoplasmic structure. 
DeELAFIELD’s haematoxylin far outclasses all the other stains used 
for total objets. It is best to stain as darkly as possible (12 to 24 
hours in 1/, strength, +/, strength, or even full strength stain) and 
then to decolorize with exceedingly dilute hydrochloric acid. The 
decolorization should be watched under the microscope and when it 
has reached the right point it can at once be stopped by adding a 
drop of weak ammonium hydrate. The decolorization should be 
carried to a point that seems extreme, for the objects become much 
darker upon adding the ammonia. A little experience enables one 
to regulate the stain very accurately. If upon adding the ammonia 
the objects are found to be too dark, most of the liquid can be 
drawn off and acid again added, the decolorization being carried to 
the desired point. It should, however, be noted that, upon adding 
acid after ammonia has been used, the decolorization is much more 
rapid than before the objects were treated with ammonia. With 
this stain used in this way preparations of total objects can be 
obtained which rival for clearness the best sections. 
The animals when stained were run through graded alcohols to 
cedar oil and were mounted in balsam. As Dretarirenp’s haematoxylin 
is exceedingly sensitive to the presence of the least acid, readily 
fading when in balsam, if this be in the least degree acid, it is 
*) For suggesting this method, which is a very useful one, I am indebted 
to Mr. W. Freytace of Wiirzburg. 
