Alga& as Geological Guides. — I nines. 1)7 
noticed by myself in various localities. They are nearly 
always accompanied by raindrop impressions, undoubted worm 
tracks, or schematic markings. The absence of other organic 
forms is almost in itself sufficient to stamp them as of inor- 
ganic origin. They occur in vast profusion, filling whole sur- 
faces of rock through many vertical feet of strata, and many 
attain a great size and length, ten or fifteen feet being nut 
unusual. 
The data upon which any chart or any scheme showing 
derivation is based is necessaril} derived from the published 
descriptions of species and genera. The more numerous these 
are the larger the amount of dataiipon which conclusions are 
based. But when a critical examination shows that there are 
more genera and species made than there is reason for. when 
it is shown that the increase of genera and species is due to 
the fact that new forms are made for no other reason than 
that they are found in different horizons, the value of the 
data depreciates very materially. When still further study 
shows that the species and genera charged to Alga- are not 
really such, the value of the deductions fades away entirely. 
Such we believe to lie the case: so that, much as we may be- 
lieve in the evolutionary theory, we do not believe it receives 
support from such deductions. This conclusion was also 
reached by Williamson in 1885 as shown in a paper read in 
that year.* In discussing problematic organisms after refer- 
ring to the diversity of opinion as to their true nature, he 
-ays that the objects "can have no weight with the student of 
evolution, aiid until we obtain more definite proofs than we 
have heretofore obtained of the vegetable nature of most of 
these dubious 'Paleozoic Algae,' we must reject their testimony 
when framing a pedigree for the vegetable kingdom. At the 
same time I regard the existence of an abundant marine vege- 
tation during the Paleozoic ages as an inevitable corollary of 
the fact that the rocks of those ages ahound in the remain- of 
phytophagous animals." (p. 2S.) 
The correlation of the strata of one country, or pari of one 
country, with another, has also been frequently made upon the 
*Williamson, W. C. On some undescribed tracks of invertebrate ani- 
mals from the Yoredale rocke, and on some inorganic phenomena pro- 
duced on tidal shores, simulating plant remains. Mem. Manchester 
Lit. and Phil. Soc, 3d ser., vol. x, pp, L9 29. 
