6 DERIVATION OF ORG.VNIC BEINGS. 



vegetable life, follo\nng on its free access. Even the oxygen 

 comes into play only as a supporter of the life of the forms 

 originating from these genns. Neither gas nor liquid, 

 neither electricity nor magnetism, nor ozone, nor anything 

 else, known or unkno^^^l, which may be present in the air, 

 save only the germs which it carries, are the essential con- 

 dition of the development of life.* 



The general result of experiments of this kind, taken in 

 conjunction with arguments from the general analogy of 

 plants and animals, have now led to the abandonment, by 

 common consent, of the theories, once so prevalent among 

 physiologists, of spontaneous generation ; for the clear in- 

 ference from these experiments is, that there exist con- 

 stantly, either in the organic matter, or, more probably, in 

 the natural air or water, multitudes of germs of many 

 different organisms, and that the speciality of the forms 

 that appear in particidar cases depends, either on the nidus 

 variously modifying the development of germs originally 

 identical, or on its so favouring the growth of some, that 

 the others are stifled, as it were, and so prove abortive. 



We have many other indications of the existence of 

 multitudes of such germs floating in the air. It is mainly 

 by the conveyance of pollen in this way that we account 

 for the fertilization of the seeds of dioecious plants ; and 

 that the spires of various species of ferns must be simi- 

 larly wafted about in their vicinity, appears from the diffi- 

 culty of obtaining pure seed to be depended on for the 

 multiplication of any particular species, many of the plants 

 raised turning out of quite a different kind from that from 

 which the spores were collected. "I* 



It is true that there are still many cases in which Natu- 

 ralists are much perplexed to account for the formation of 

 organized beings, if the idea of their origination indepen- 



* Op. Cit. pp. 85-89. 

 t Dr. Balfour, in Edin. N. Phil. Jouru. VIII., 278. 



