562 FRAGMENTS OF SCIENCE. 
CHAPTER XXXV. 
SPONTANEOUS GENERATION.* 
WITHIN ten minutes' walk of a little cottage which I 
have recently built in the Alps, there is a small lake, fed 
by the melted snows of the upper mountains. During the 
early weeks of summer no trace of life is to be discerned in 
this water; but invariably toward the end of Julv, or the 
beginning of August, swarrns of tailed organisms are 
seen enjoying the sun's warmth along the shallow margins 
of the lake, and rushing with audible patter into deeper 
water at the approach of danger. The origin of this 
periodic crowd of living things is by no means obvious. 
For years I had never noticed in the lake either an adult 
frog, or the smallest fragment of frog spawn; so that were 
I not otherwise informed, I should have found the conclu- 
sion of Mathiole a natural one, namely, that tadpoles are 
generated in lake mud by the vivifying action of the sun. 
The checks which experience alone can furnish being 
absent, the spontaneous generation of creatures quite as 
high as the frog in the scale of being was assumed for ages 
to be a fact. Here, as elsewhere, the dominant mind of 
Aristotle stamped its notions on the world at large. For 
nearly twenty centuries after him men found no difficulty 
in believing in cases of spontaneous generation which would 
now be rejected as monstrous by the most fanatical sup- 
porter of the doctrine. Shell fish of all kinds were con- 
sidered to be without parental origin. Eels were supposed 
to spring spontaneously from the fat ooze of the Nile. 
Caterpillars were the spontaneous products of the leaves on 
which they fed; while winged insects, serpents, rats, and 
mice were all thought capable of being generated without 
sexual intervention. 
The most copious source of this life without an 
ancestry was putrefying flesh; and, lacking the checks 
imposed by fuller investigation, the conclusion that flesh 
possesses and exerts this generative power is a natural one. 
I well remember when a child of ten or twelve seeing a 
joint of imperfectly salted beef cut into, and coils of mag- 
gots laid bare within the mass. Without a moment's 
* The Nineteenth Century, January, 1878. 
