the "Philosophie Zooelogique." In this
treatise he taught that the animal kingdom is a unit and that all its
members are blood relations; that the members vary with varying
conditions; that this variation results in continued advance. In all
of these points Lamarck is at one with modern thought. His idea of the
method by which the variation comes about has been accepted and
rejected; modified, reaccepted, and again rejected.

Lamarck's conception of the cause of progress was somewhat as follows:
The desire for any action on the part of an animal leads to efforts to
accomplish that desire. From these efforts came gradually the organ
and its accompanying powers. With every exercise of these powers the
organ and its corresponding function became better developed. Every
gain either in function or in organ was transmitted to those of the
next generation, who were thus enabled to start where their parents
left off. The general environment constantly gave the stimuli that led
to the adaptive changes.

American zooelogists have been especially inclined toward Lamarck's
ideas. Until Weissmann startled the scientific world with his sharp
denial of the possibility of transmitting to offspring any growth
acquired by the parents, all seemed well. There is a tendency now to
insist once more that slowly and gradually, in some perhaps as yet
unexplained way, external factors do influence even egg cells, and
gradually acquired characters do reappear in the offspring.

The blighting setback these views suffered came from the criticisms of
Baron Cuvier. This genuinely remarkable man had built up the study of
comparative anatomy. To him students flocked from all sides. Among
these one of the most brilliant was Agassiz, the Swiss naturalist, who
later came to this country, filled with Cuvier's ideas. This great
teacher believed that species are fixed. He knew better than any man
of his times the wonderful similarity in structure between animals of
a given class. He attributed this not to any real blood relationship
between the animals. They were alike because they had been made by the
same Creator. This great Artificer worked along four main lines, and
hence animals could be divided into four groups. Many who have studied
text books on zooelogy written in this country by Agassiz and his
followers will remember the four classes--Radiates, Articulates,
Mollusks, and Vertebrates. Agassiz was such a wonderful teacher and so
genial and so lo