AUGUST WEISMANN 
Born January 17, 1834, died November 5, 1914 
By Frank R. Lillie 
Professor of Zodlogy at the University of Chicago 
HE life of Professor Weismann 
a spanned the most interesting 
and important period in the 
history of biology. In his early child- 
hood Schleiden and Schwann established 
the cell theory (1838-1839); he was a 
young man of twenty-five at the time 
of publication of Darwin’s Origin of 
Species (1859). During his active life 
as zodlogist were discovered those great 
principles concerning cell-division, the 
fertilization of the egg and the history of 
the germ-cells, which he applied with 
such success to the theory of heredity. 
He participated in the grand struggle 
over the evolution theory and the factors 
of evolution during the latter half of the 
nineteenth century; he witnessed the 
rise of experimental zodlogy and in his 
old age came the period of exact research 
in genetics, which his own studies had 
done much to prepare. 
The last weeks of his life were sad- 
dened by the great war. He had liveda 
long life full of loving and disinterested 
labor, crowned by many honors and the 
universal respect of the scientific world. 
An immense pathos inheres in his last 
public act —the relinquishment of the 
academic honors bestowed on him in 
England. 
Like so many of the zodlogists of his 
time Weismann studied medicine, but 
he found opportunity during the short 
period of its practice to carry out z06- 
logical investigations on the life history 
and especially the post-embryonic devel- 
opment and metamorphosis of flies. In 
1863 he became attached to the Uni- 
versity of Freiburg, and spent the re- 
mainder of his life, fifty-one years, in 
this quiet provincial University, in spite 
of offers from larger universities. Here 
he found the leisure and the quiet 
beautiful surroundings in which he could 
devote himself heart and soul to investi- 
gation and reflection. His objective in- 
vestigations were limited by serious 
trouble with his eyes which began in the 
seventies, and later compelled him to 
relinquish the microscopical studies for 
which he had such unbounded enthu- 
siasm. His vision was thus turned more 
and more inward to constructive think- 
ing; it was no doubt in part due to this 
physical handicap that we owe his great 
theoretical generalizations. 
Weismann was a true naturalist, who 
viewed nature with a loving enthusiasm 
which appears clearly in the objective 
researches in zodlogy of the first fifty 
years of his life. His main contributions 
are classical in their mastery of detail, 
wealth of observation and broad outlook. 
His earliest studies were physiological 
and histological (1858-1862). Then fol- 
lowed a series of papers on the embryonic 
and post-embryonic development of flies 
(1862-1866). Studies on the seasonal 
dimorphism of butterflies next engaged 
his attention in which he raised questions 
that led to later fundamental researches 
by other investigators. In 1875 he 
began a long series of studies on the 
natural history and reproductions of 
Daphnids (continued to 1889) which 
constitute the foundation of all subse- 
quent study on this group and were 
especially important for the funda- 
mental problems of parthenogenesis, sex- 
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