LTinrEAN SOCIETY OF LONDON. liii 



his views of the " Beginnings of Life " is announced ; but I have not 

 yet seen it. 



If, then, spontaneous generation may as a theory in the minds 

 of some persons have become referred to the class of paradoxes like 

 the quadrature of the circle, yet it is still supported by so many na- 

 turalists whose opinions are entitled to consideration, and there is so 

 much to be said for as well as against it which appears unsusceptible 

 of direct and positive proof, that it is likely to be long maintained 

 as a subject of controversy, without any further much more definite 

 result. But there is one question of a more practical nature, often 

 supposed to be connected with it, which has excited, and is still 

 calliiag for the serious attention of men of science, experience, and 

 judgment, as well as of various Governments. I allude to those 

 parasitical scourges which within the last thirty years have made 

 such havoc in several important articles of European food and in- 

 dustry. Thirty years since, and, I believe, up to the fatal year 1845, 

 the potato-disease, the silkworm -pebrine, and the oidium of the 

 vine were unknown in Europe ; and we can most of us remember 

 how the sudden appearance and rapid extension of each in succes- 

 sion produced the famine in Ireland, and the ruin of so many French 

 and Italian silk-breeders and wine-growers of the Mediterranean 

 region, Madeira, and Bordeaux, and how long men of science have 

 been baffled in their efforts at ascertaining the true history of the 

 attendant fungi and devising an efficacious remedy. The potato- 

 disease appears now to have settled down into one of those chronic 

 epidemics whose varying intensity, according to season and other 

 circumstances over which we have little control, must enter into the 

 calculations of every potato -grower. This useful tuber can no 

 longer, indeed, be advantageously cultivated in that wholesale manner 

 which induced the late Thomas Andrew Knight and others to attach 

 to it so high an economic value ; but it may now again be fairly de- 

 pended upon as an important article of household food. The pebrine 

 of the silkworm, from the latest reports I have seen of the commis- 

 sions of Lyons and other places, shows but little abatement of its 

 intensity, although it has in some measure changed its character, 

 and is, it is to be feared, through the carelessness or cupidity of in- 

 terested dealers, spreading even into those eastern regions which 

 have been looked to for the supply of " seed " free from the fatal 

 germ. The oidium, on the contrary, has been got more under con- 

 trol ; and experience now shows that, in many districts at least, its 

 ravages can be checked or entirely stopped by means within the 



