46 Lectures on Bacteria. [§ v. 



ficial observer is led to assume in such cases that they owe their 

 origin to other bodies present at the particular place before their 

 appearance there, no matter what these bodies may be, and not 

 to germs formed from similar parents. Such views were not 

 unnatural in ancient times. Virgil's (16) account of the pro- 

 duction of a swarm of bees from the buried entrails of a steer 

 furnishes an obvious illustration, and shows how utterly defective 

 were the observation and reasoning which admitted of such 

 notions. With a closer observation of nature it became evident 

 in one case after another that the appearance of the particular 

 organisms invariably commenced with germs which were the 

 product of parents of the same kind, and that the point not 

 observed was how these germs found their way to the place of 

 observation. Generation without parents was step by step driven 

 into a corner. The process began with large and coarse objects 

 like the maggots of flies which appear in carrion, not by spon- 

 taneous generation, but produced from the ova of flies which 

 have been deposited in it. And as the adherents of the old 

 doctrine were driven back on smaller objects, such as moulds, 

 the lowest forms of animal life and the hke, their refutation 

 followed step by step with equal success in these domains also. 

 Microscopic and improved experimental methods by turns 

 sharpened the weapons. Thus we find ourselves face to face 

 with the fact that the adherents of generation without parents, 

 at'least during the last hundred years, seek for support to their 

 doctrine always in the minutest and at the time the most inac- 

 cessible objects. The view has never been entirely given up, and 

 for two good reasons. First, because an opinion once expressed 

 or put into print, be it what it may, never totally disappears ; the 

 second and much better reason is, that we must necessarily assume 

 that organisms were certainly once produced without germs and 

 without parents ; the possibility that this may happen again at 

 any time must be allowed, and to prove that this does happen and 

 to show where and how it happens would be highly interesting, 

 and a really worthy subject for the efforts of the enquirer. 



