APPENDIX B. XXIX 



ance then between the organisms which would appear to 

 have been produced de novo within the previously-heated 

 experimental tubes, and those which come from the cavities 

 within the crystals. The conditions are unfavourable in 

 both cases, and the products which result seem to be very 

 slowly evolved. 



Because, therefore, of the close resemblance which must 

 obtain between the mode of formation of the first and of subse- 

 quent particles of one of the simplest organisms ; because 

 tartrate of ammonia seems especially and peculiarly prone to 

 lapse into living modes of combination ; because, in addition 

 to the evidence with respect to this particular change, isomeric 

 re-arrangements of other complex substances are undoubtedly 

 capable of taking place ' spontaneously' without the agency 

 of pre-existing living matter; and because the organisms 

 found in the crystals are actually similar to those which form 

 de novo in the experimental flasks, — for all these reasons 

 combined, I deem it to be more probable that the filaments 

 and spore-like bodies found within the crystals of ammonic 

 tartrate, have been slowly developed from specks of newly- 

 evolved living matter, than that they have had any other mode 

 of origin. If it had not been proved that living matter could 

 form de novo, there would not be sufficient reason for believing 

 that it had occurred in this particular case; so that those 

 who are still unconvinced upon the general question will, 

 of course, not be much influenced by the evidence now 

 adduced. 



