greatest service to biology to consist. The
attitude, however, seems to smack of vitalism, and Roux, as we have
seen, is no vitalist. He holds that the marvellous and apparently
purposive tissue-qualities which underlie all processes of functional
adaptation have arisen "naturally," in the course of evolution, by the
action of natural selection upon the various properties, useful and
useless, which appeared fortuitously in the primary living organisms. He
is, moreover, deeply imbued with the materialistic philosophy of his
youth, and it is indeed one of the chief characteristics of his system
that he states the fundamental properties or qualities of life in terms
of metabolism. A vital quality is for Roux a special process or mode of
assimilation. The faculty of "morphological assimilation" whereby form
is imposed upon formless chemical processes is the ultimate term of
Roux's analysis--"the most general, most essential, and most
characteristic formative activity of life" (p. 631, 1902).

We have now to consider very briefly the early results achieved by
Roux's fellow-workers in the field of causal morphology. As D. Barfurth
points out,[488] the years 1880-90 saw a general awakening of interest in
experimental morphology, and it is hard to say whether Roux's work was
cause or consequence. "There fall into this period," writes Barfurth,
"the experimental investigations by Born and Pflueger on the sexual
difference in frogs (1881), by Pflueger on the parthenogenetic
segmentation of Amphibian ova, on crossing among the Amphibia, and on
other important subjects (1882). In the following year (1883) appeared
two papers of fundamental importance, by E. Pflueger and W. Roux: Pflueger
publishing his researches on 'the influence of gravity on
cell-division,' Roux his experimental investigations on 'the time of the
determination of the chief planes in the frog-embryo.'... In the same
year appeared A. Rauber's experimental studies 'on the influence of
temperature, atmospheric pressure, and various substances on the
development of animal ova,' which have brought many similar works in
their train. The following year (1884) saw a lively controversy on
Pflueger's gravity-experiments with animal eggs, in which took part
Pflueger, Born, Roux, O. Hertwig and others, and in this year appeared
work by Roux dealing with the experimental study of development, and in
particular giving the results of the first definitely localised
pricking-exp