CHARLES DARWIN—WEISMANN. 444 
just in the same way as the parts of the body and the mental 
faculties. For thirty-two years he followed out this idea, experi- 
menting, observing, collecting facts, until finally he was able to write 
his remarkable and fascinating book, the first English edition of 
which consisted of 5,000 copies. 
Darwin’s next book appeared in 1875, and this also had been a 
long time in course of preparation. In ranging about the country 
during a summer holiday in 1860 he had noticed a dainty little plant, 
the “sundew ” (Drosera rotundifolia), to the viscous leaves of which | 
several small insects were usually found adhering. Many other 
collectors had noticed this, because of the difficulty of procuring 
a clean specimen for the herbarium. Darwin took a few of the 
plants home with him, and soon discovered that certain parts of the 
leaves exhibit movement as soon as small insects are brought into 
contact with them. This led him to the discovery of “ Insectivorous 
Plants,” and his book bearing that title was published fifteen years 
later. 
In 1876 Darwin published a work on “ Different Forms of Flowers 
on Plants of the Same Species,” and in 1880, jointly with his son 
Francis, “The Movements of Plants.” Finally, in 1881, the year 
before his death, there appeared “The Formation of Vegetable 
Mould through the Action of Worms.” This last book, lke some 
of the earlier short treatises, had no direct connection with the theory 
of evolution, but it illustrates in a very characteristic manner Dar- 
win’s eminently scientific mood, which led him to note everything 
that seemed unusual or interesting in the most ordinary things, and 
to follow it out till it led him on to new discoveries. How many 
hundreds of people, and even of naturalists, had seen the little earth- 
castings that cover the damper parts of our garden paths on summer 
mornings! These are due to earthworms, and are the remains of 
the decaying leaves on which they feed. The earthworms cover the 
whole land with fertile mold, and through their agency in the course 
of time the surface of the ground is raised, and bad soil is trans- 
formed into good. 
But no one had deemed the phenomenon worthy of attention.* 
It is a case parallel with that of the sundew, which hundreds of 
botanists had passed by without ever suspecting that the adherence 
of the insects was more than a matter of chance. 
The fruitful discovery of the “struggle for existence,” too, was 
due to this vision of the true naturalist, who sees in what lies before 
him much that others pass by unheeding. It was certainly no chance 
“Tn regard to the earthworm, I must note that my countryman, Professor 
Hensen, the excellent zoologist of Kiel, displayed the same acuteness of obser- 
. vation and drew the same conclusions from the castings at the same time as 
Darwin did. 
