1^2 Appendix. 



for a season, or even for a period of years, and when finally de- 

 veloped the parent animals have long since disappeared from the 

 face of the earth, and hence an easy belief in a new or spon- 

 taneous generation.* Gradually, however, after years and even 

 centuries of patient investigation, all these and the kindred diffi- . 

 culties have been removed and the errors have been explained, so 

 that even during this first epoch some of the supposed cases of 

 spontaneous generation were removed from this category, and 

 explained in accordance with the increased light thus gained. 

 This brief survey of the first epoch in the history of spontaneous 

 generation must suffice. Indeed, thus much of reference to it is 

 only pardonable, for the purpose of contrasting the opinions 

 then prevailing among scientific men, with the more positive 

 knowledge which now obtains. 



2d Epoch. The first solid and experimental advance toward 

 the positive knowledge of to-day, and the first distinct repudia- 

 tion of the doctrine of spontaneous generation, was made in 

 1668, by Francesco Redi, the Italian naturalist.f " He did not 

 trouble himself," says Huxley,** "with speculative considera- 

 tions, but attacked experimentally what had been considered to 

 be particular cases of spontaneous generation." He directed his 

 attention first to studying the origin of maggots in putrefying 

 meat. He observed that before the appearance of such maggots 

 flies were invariably to be seen hovering about and alighting 



* " A remarkable instance of this is the case of the American seventeen- 

 year locust (Cicada septendecim), where a period of seventeen years elapses 

 between the hatching of the larva and the appearance of the perfect insect; 

 the larva all this time remaining buried in the ground, while the life ol the 

 insect in its perfect state does not last over six weeks. A brood of these 

 locusts appeared in the city of New York and its immediate vicinity in 1843, 

 and again in 1860. If they return with their accustomed regularity, their 

 next appearance will be in 1877."— Dalton : Joe. cit. 



t Francesco: An Italian physician, 162()-1697, distinguished alike for his 

 attainments in literature and in natural history. His writings have been 

 collected and published in a single volume. Opuscoli di Storia Naturale. 

 Florence, 1858. 



** President's Address to British Association, at Liverpool, Sept., 1870. This 

 address has been published in many journals, and also in separate form. 

 yatiirc, Sept. 15, 1870, p. 400, 



