CHAPTER XVIII. 



THE PANSPERMIC HYPOTHESIS. 



Reasons why this subject has been deferred. Has more to do with 

 Heterogenesis than with Archebiosis. Why ' Germs * were supposed 

 to be necessary. L'Emboitement and Panspermism — Bonnet and 

 Spallanzani. Their views founded on Fancy rather than Fact. 

 M. Pasteur's observations as to presence of Germs in the Air. His 

 so-called 'corpuscles organises.' His modifications of Panspermic 

 Theory. M. Pouchet's observations as to Nature and abundance 

 of Solid Bodies in the Atmosphere. Work of other Observers. 

 Probabilities of the case. M. Pasteur's Assumptions. Difficulty of 

 explaining Facts in accordance with the Panspermic Doctrine. 

 Mode of origin of Ciliated Infusoria not affected by its Truth or 

 Falsity. Modes of Reproduction of Ciliated Infusoria. Fission. 

 Development of Ova. Comparative Experiments with different 

 Fluids similarly exposed. Occurrence or non-occurrence of Infusoria 

 dependent upon Will of Experimenter. Influenced by thickness of 

 Pellicle. Also influenced by Nature of Infusion. Presence and 

 kinds of Organisms proved to be more dependent upon this than 

 upon Germs in Air or Water. Reasons for referring especially to 

 Origin of Ciliated Infusoria rather than that of Fungi. These 

 proceed from large and easily recognizable Germs. Utterly un- 

 tenable nature of Panspennic Hypothesis. 



WE have already shown that the de novo origin 

 of living matter can be established without 

 reference to investigations concerning the number or 

 nature of the germs contained in the atmosphere. 

 With the view of avoiding all chances of error, we 



