2 THE AMERICAN NATURALIST. [VOL. XXXII. 
fying result of this persistency is that at last material has been 
found which is accessible to modern refined preparative methods 
and to microscopic analysis. 
Giimbel (78) was the first to isolate stipes imbedded in lime- 
stone. Later Tornquist (90, '92) obtained much valuable infor- 
mation by grinding pyritized material. The best results, 
however, have been obtained by the methods employed lately 
by Holm (90,'95) and Wiman (93,’95). For the details of 
these preparative methods, the reader is referred to Wiman’s 
interesting account in his paper, “ Ueber die Graptoliten ” ('95), 
the review (96) of his work in the American Geologist, and to 
Wiman’s “ Structure of the Graptolites’’ (96). 
Both Holm and Wiman isolated stipes by dissolving the matrix. 
Various acids have been used for dissolving, according to the 
nature of the rock. Limestone material was found the simplest 
to handle, and muriatic acid in different states of solution or 
milder solvents, such as acetic acid, gave good results. Espe- 
cially interesting to American readers is the description which 
Wiman gives of his treatment of highly aluminous clay slates, as 
these are almost the only graptolite-bearing rocks found here. 
Wiman subjected them to the successive action of acetic and 
hydrofluoric acids. J. M. Clarke handled similar material 
successfully with acids and caustic potash. These methods, 
however, fail with a matrix that does not contain a sufficient 
lime-content.to lose its consistence by the dissolution of the 
latter, and this appears to be the case with most of the Ameri- 
can graptolite-bearing rocks. Wiman had also occasion to isolate 
graptolites from chert-masses by successively subjecting the 
rock to a treatment with concentrated hydrofluoric acid and 
muriatic acid. 
The isolated graptolites have been decolored both by Holm 
and Wiman in different ways. Wiman used first Schultze’s 
maceration medium, which is a solution of calcium chlorate in 
nitric acid, but later substituted for it eau de Javelle or potas- 
sium hypochlorite, because Schultze’s medium is often too 
harsh. The specimens were then cleared with chloroform or 
other clearing fluids and mounted in Canada balsam, or, where 
this method could not be used on account of the thickness of 
