244 THE president's address, 



trically opposite opinions are stoutly maintained by their respective 

 adherents. 



On the one hand the Panspermists assert that every living 

 thing, no matter how minute in size, how simple in form, and 

 how low in organization, originates from some similar living thing. 

 Omne vivum ex ovo is their physiological shibboleth. Every living 

 thing is developed from a living germ, and therefore if living things 

 are found in decomposing infusions the living germs must have been 

 h ere previously. Such is their method of reasoning. It is useless to 

 point to experiments in which infusoria have been found to appear in 

 infusions in which all traces of previously existing life have been 

 destroyed, and from which all fresh germs have been rigorously 

 excluded. To the Panspermists the appearance of living organisms 

 proves the previous existence, or subsequent entrance, of living 

 genus. " Without such living germs," they ask, " how can the 

 living organisms become developed ?" 



On the other hand, the Heterogenists repudiate all dogmas, and 

 rely upon their experiments and observations. They subject in- 

 fusions of vegetable and animal matter to a sufficiently high tem- 

 perature to destroy all life. They exclude air and the germs that 

 it may contain, either by hermetically sealing the vessels with which 

 they experiment, or by interposing tubes filled with sulphuric acid. 

 They watch, and find that in spite of all their precautions the in- 

 fusions, if exposed to light and warmth, sooner or later become 

 filled with living organisms. " Whence come these ?" they trium- 

 phantly ask. " How do they arise, if not by a process of sponta- 

 neous generation ?" 



Thus the Panspermists and the Heterogenists contend for their 

 respective positions. The battle is fought with all the warmth and 

 feeling of a polemical or theological controversy, rather than with 

 the calmness and candour proper to a scientific discussion. 



It would be altogether out of place for me to attempt, on this 

 occasion, to give you even a bare sketch of the history, progress, 

 and present aspects of the controversy.* And I certainly shall not 



* I would refer those who may read this address to a very able series of articles 

 that have appeared in the " British Medical Journal" for the present year, on 

 the " Origin of Life," and also to the original papers of Pasteur, Pouchet, Jolly, 

 Musset, Mantegazza, and others, communicated to the French Academie des 

 Sciences, and especially to Dr. Bennett's recent contribution to the " Popular 

 Science Review," Jan., 18f)9, on the " Molecular Origin of Infusr'ia." Mr. 

 Herbert Spencer's appendix to the first volume of his "Principles ol Biology" 

 must also claim attention. A resume' of the whole discussion has been published 

 by M. Pennelieu, in an independent work entitled " L'Origine de la Vie." 

 Paris. 1868. 



