inations of Fries are not conclusive. He himself often confesses
as much. The microscopic technique of that day did not yield the data
needful for minute comparison among these most delicate forms.

It remained for DeBary and Rostafinski to introduce a new factor into
the description of species, and by spore-measurement and the delineation
of microscopic detail to supply an element of definiteness which has no
parallel in the work of any earlier student of this group. Under these
conditions the revision undertaken by Rostafinski was of a most heroic
sort. His work was almost a new beginning; and while in nomenclature he
was inclined to follow the Paris Code, yet the inadequacy of the earlier
descriptions often made such a course impracticable. The synonymy of
Rostafinski is largely that of Fries, and upon this the Polish author
attempts to apply the law of priority. In the historical note, _wzmianka
historyczna_, accompanying the description of each specific form, he
generally states the reason for the nomenclature he adopts, whether
selected from the mass of supposed synonymy or introduced by himself _de
novo_. Unfortunately, Rostafinski is sometimes purely arbitrary in his
selections. He sometimes changes a specific or even generic name,
otherwise correctly applied, simply because in primary etymological
significance the name seems to him inappropriate. In such cases it is
proper to restore the earlier name. Nevertheless Rostafinski is still
our most trustworthy guide.

Of course, where later investigations have served to obliterate the
once-thought patent distinctions between supposed genera or species, it
is proper to unite such forms under the older determinable titles and
this we have attempted. But wherever in the present work a name has been
changed, the name of the earlier author will be found in parenthesis,
followed immediately by that of him who made the change, and in general,
recent practice, especially as expressed in the rules of the various
codes, has determined the puzzling questions of nomenclature.

In justification of the use of _Myxomycetes_ as a general title it may
be said that in this case prevalent usage is not inconsistent with a
rational application of the rules of priority. The Friesian designation
_Myxogastres_ was applied by its author in 1829 to the endosporous
slime-moulds as a section of gasteromycetous fungi. Four years later
Link, perceiving more clearly the absolute distinctness of