SPONTANEOUS GENERATION 247 



1. Containable fluids, such as atmospheric air, various gases, water, 

 €tc. The nature of these fluids does not permit them to pass through 

 the walls of the containing parts, but only to go in and escape through 

 the exits ; 



2. U ncontainable fluids, such as caloric, electricity, etc. These 

 subtle fluids are naturally capable of passing through the walls of 

 investing membranes, cells, etc., and hence cannot be retained or pre- 

 served by any body, except for a brief period. 



From the principles set forth in this chapter, it appears to me certain 

 that nature does herself carry out spontaneous or direct generations, 

 that she has this power, and that she utiUses it at the anterior extremity 

 of each organic kingdom, where the most imperfect living bodies are 

 found ; and that it is exclusively through their medium that she has 

 given existence to all the rest. 



To me then it seems a truth of the highest certainty, that nature 

 forms direct or so-called spontaneous generations at the beginning of 

 the plant and animal scales. But a new question presents itself : is it 

 certain that she does not give rise to similar generations at any other 

 point of these scales ? I have hitherto held that this question might 

 be answered in the affirmative, because it seemed to me that, in order 

 to give existence to all hving bodies, it was enough for nature to have 

 formed directly the simplest and most imperfect of animals and 

 plants. 



Yet there are so many accurate observations, so many facts known, 

 which suggest that nature does form direct generations elsewhere than 

 at the beginning of the animal and vegetable scales, and we know that 

 her resources are so wide and her methods so varied in difl'erent cir- 

 cumstances, that it is quite possible that my view, according to which 

 the possibiUty of direct generations is limited to the most imperfect 

 animals and plants, has no true foundation. 



Why indeed should nature not give rise to direct generations at 

 various points in the first half of the animal and plant scales, and even 

 at the origin of certain separate branches of these scales ? Why should 

 she not establish, in favourable circumstances, in these diverse rudi- 

 mentary living bodies, certain special systems of organisation, different 

 from those observed at the points where the animal and vegetable 

 scales appear to begin ? 



Is it not plausible, as able naturalists have beHeved, that intestinal 

 worms which are never found except in the body of other animals, 

 are direct generations of nature ; that certain vermin, which cause 

 diseases of the skin or pullulate there as a result of such diseases, also 

 have a similar origin ? And why should not the same hold good among 

 such plants as moulds, the various fungi, and even the lichens, which 



