SPONTANEOUS GENERATION. 45 



which finally appear in the infusion are produced spontane- 

 ously out of the molecular pellicle, the molecules of which are 

 also of spontaneous origin, and are not derived from any pre- 

 existing germs. 



b. By the " panspermists," or the opponents of spontaneous 

 generation, it is alleged, on the other hand, that the produc- 

 tion of Bacteria, Vibrios, Monads, and Infusoria, in organic 

 infusions, is due simply to the fact that the atmosphere, and 

 probably the fluid itself, is charged with innumerable germs 

 too minute, perhaps, to be always detectable by the micro- 

 scope which, obtaining access to the fluid, and finding there 

 favourable conditions, are developed into living beings. 



A large number of elaborate experiments have been carried 

 out to prove that atmospheric air is absolutely necessary for 

 the production of these living beings, and that if the air be 

 properly purified by passage through destructive chemical 

 reagents, no such organisms will be produced, provided that 

 the infusion have been previously boiled. As the results of all 

 these experimental trials have hitherto proved more or less 

 contradictory, it is unnecessary to enter into the question fur- 

 ther, and it will be sufficient to indicate the following general 

 considerations : 



a. The primary molecules which appear in the fluid are ex- 

 tremely minute, and if they are developed from germs, these 

 may be so small as to elude any power of the microscope yet 

 known to us. As they subsequently become converted into 

 bacteria and vibrios, and as there can be little dispute as to 

 these being truly living organisms, we are obliged to believe 

 that they must have had some definite origin. It appears, 

 however, to be hardly philosophical to assume that they form 

 themselves out of the inorganic materials of the infusion ; since 

 this implies the sudden appearance, or creation, of new force, 

 for which there seems to be no means of accounting. 



b. The nature of the vibrios must be looked upon as un- 

 certain. To say the least of it, they are quite as likely to be 

 plants as animals; and the most probable hypothesis would 

 place them near the filamentous Confervae, or would regard 

 them as the mycelium of various species of Moulds (Penicil- 

 lium\ The bacteria are undoubtedly of a vegetable nature, 

 and referable to the Algce. 



c. What has been said above with regard to the origin of 

 the bacteria and vibrios applies equally to the origin of the 

 Monads, which appear in the infusion subsequently to the 

 death of the vibrios. 



d. These monads, as shown by recent researches, are pro- 



