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R
R i c u a r d C l a y Sl S o ììs , L im i t e d ,
L o n d o n & 13un(5ay.
PREFACE.
The preparation of a monograph dealing with minute organisms,
where the descriptions of the old authors are comparatively
or often absolutely valueless, depends on the facilities
afforded for a critical examination of type or authentic specimens.
In this respect I have enjoyed exceptional facilities.
The splendid collection of Myxogastres in the. Royal Herbarium,
Kew, rich in types, and with numerous annotations by Rosta-
finski, who examined the collection in detail, and which indeed
served as the basis for his excellent monograph, also served me
in like manner. To other workers in the same field in different
countries I am also indebted for the loan or gift of valuable,
and in some instances unique, specimens. To all who have in
this or other ways assisted, I offer my sincere thanks.
Notwithstanding the excellent work initiated by the late
Professor De Bary, and continued by Brefeld, Cienkowski,
Woronin, Zopf, and others, the life-history of the majority of
forms is still unknown; hence all attempts at classification, as
also the conception as to what constitutes a species, must be
considered as tentative. When we are better aquainted with
the main lines of development and lines of variation, also the
conditions determining these variations, it is certain that the
main factor in the discrimination of species will not be a one-
twelfth oil-immersion objective.
Geo. Massee.
Kew, 1892.