CHAPTER VII. 



MODE OF ORIGIN OF PRIMORDIAL LIVING THINGS! 

 NATURE OF PROBLEM. 



Changes which occur in an Organic Infusion. Evolution of Gas. 

 Plastide-particles and Bacteria. Formation of ' Pellicle.' Mode 

 of formation of Bacteria. Views as to their nature. Different 

 kinds of Bacteria and allied organisms Vibriones, Leptothrix, and 

 Spirillum. Composition of proligerous pellicle.' Views of Cohn 

 and Pouchet. Sometimes no ' pellicle' forms, only turbidity, flocculi, 

 or deposit. Mode of origin of Torula. Views of Hallier. Micro- 

 cocci, cryptococci, and arthrococci. Their mutual relations to one 

 another and to Fungi. Nature and mode of origin of Sarcina. 

 Development of Fungus ' spores.' Doubt as to mode of origin of 

 these forms. Useless to look in Air for germs of Bacteria. Mode 

 of appearance of these in thin films of fluid. Only two explanations 

 possible. Origin either germless or from invisible germs. Existence 

 of latter must not be recklessly postulated. Similar problem in case 

 of origin of Crystals. Statical and dynamical aggregates. Solution 

 of problem concerning Crystals. Mr. Rainey's observations. Micro- 

 scopical evidence similar in both cases. This can neither confirm 

 nor invalidate the supposition as to invisible germs, crystalline or 

 living. The existence of both equally hypothetical. 



WHEN a fluid containing an organic substance in 

 solution is allowed to remain in contact with 

 air during moderately warm x weather, it soon undergoes 



1 Fermentation usually ceases in an organic solution when the tem- 

 perature falls to about 45 F. ; and it is interesting to find that the poetic 

 imagination of Ovid had, by a kind of happy guess, led him to attach 



