The President's Address. By Eev. W. H. Bollinger. 183 



and specific results ; and while even infusions of proteid substances 

 may be exhaustively fermented by saprophytic Bacteria, the most 

 important of all ferments — that by which nature's dead organic 

 masses are removed — is one which is brought about by the successive 

 vital activities of a series of adapted organisms, which are for ever at 

 work in every region of the earth. 



There is one other matter of some interest and moment on which 

 I would say a few words. To thoroughly instructed biologists such 

 words will be quite needless : but in a Society of this kind, the possi- 

 bilities that lie in the use of the instrument are associated with the 

 contingency of large error, especially in the biology of the minuter 

 forms of life, unless a well-grounded biological knowledge form the 

 basis of all specific inference, to say nothing of deduction. 



I am the more encouraged to speak of the difficulty to which I 

 refer, because I have reason to know that it presents itself again and 

 again in the provincial Societies of the country, and is often adhered 

 to with a tenacity worthy of a better cause. I refer to the danger 

 that always exists, that young or occasional observers are exposed to, 

 amidst the complexities of minute animal and vegetable life, of con- 

 cluding that they have come upon absolute evidences of the transforma- 

 tion of one minute form into another ; that, in fact, they have 

 demonstrated cases of Heterogenesis. 



This difficulty is not diminished by the fact that, on the shelves of 

 mobt Microscopical Societies there is to be found some sort of litera- 

 ture written in support of this strange doctrine. 



You will pardon me for allusion to the field of inquiry in which I 

 have spent so many happy hours. It is, as you know, a region of 

 life in which we touch, as it were, the very margin of living things. 

 If nature were capricious anywhere, we might expect to find her so 

 here ; if her methods were in a slovenly or only half-determined con- 

 dition, we might expect to find it here. But it is not so. Know 

 accurately what you are doing ; use the precautions absolutely essen- 

 tial, and through years of the closest observation it will be seen that 

 the vegetative and vital processes generally, of the very simplest and 

 lowliest life-forms, are as much directed and controlled by immutable 

 laws as the most complex and elevated. 



The life-cycles, accurately known, of monads, repeat themselves as 

 accurately as those of Rotifers or Planarians. 



And, of course, on the very surface of the matter the question pre- 

 sents itself to the biologist why it should not be so. The irrefragable 

 philosophy of modern biology is that the most complex forms of 

 living creatures have derived their splendid complexity and adapta- 

 tions from the slow and majestically progressive variation and survival 

 from the simpler and the simplest forms. If, then, the simplest forms 

 of the present and the past were not governed by accurate and un- 

 changing laws of life, how did the rigid certainties that manifestly 

 and admittedly govern the more complex and the most complex come 

 into play ? 



