y and diverse
attempts have been made to explain the origin of species on other
principles. Names of men, like M. Wagner, Naegeli, Wigand, Koelliker,
and Kerner mark these attempts; but of these investigators Naegeli
alone proposed a well-developed hypothesis. Finally, however, Eimer,
professor of zoology in Tuebingen came forward with a detailed theory
of Descent. As early as 1888 he published a comprehensive work dealing
with it, under the title: "The Origin of Species by Means of the
Transmission of Acquired Characters According to the Laws of Organic
Growth." As the title itself indicates, a very marked divergence was
even at that time manifesting itself between Eimer and his former
teacher and friend, the great defender of Darwinism in Germany, Aug.
Weismann, professor of zoology in Freiburg in Breisgau. For, while the
latter vigorously attacks the transmission of acquired characters,
Eimer's whole theory is founded on this very transmission. Observations
regarding the coloring of animals, in fact, form the basis of Eimer's
theory.

Eimer attributes the origin of species to "organic growth" by which he
means not merely increase in size, but also change of form, etc. This
growth does not proceed blindly or aimlessly, but proceeds on rigidly
determined lines, which depend upon the structure and constitution of
the particular organism. External influences, however, also affect it.
Eimer specially emphasizes four points in this connection: 1. This
rigidly determined development of a character exhibits well defined,
regular stages, and the evolution of each individual repeats the whole
series of transformations (the Mueller-Haeckel "biogenetic-law.") 2.
New characters are first acquired by strong adult males (the law of
male dominance). 3. New characters appear on definite parts of the
body, spreading especially from the rear to the front, (the law of
undulation). 4. Varieties are stages in the process of development,
through which all the individuals of the respective species must pass.

These points indicate how important for Eimer is the transmission of
those characters which the parents themselves have acquired in the
course of their own development. He conceives that this transmission
takes place when the causative influences exert themselves permanently
on many succeeding generations. Eimer thinks that in this way the
constitution of the respective species is gradually transformed.
Besides the effect of external