128 Experiments on the Development of Bacteria, &c. 



In conclusion, we would point out that failure in manipulation, 

 contamination in unsuspected ways, such as that due to the pre- 

 servative influence of lumps, and, again, the mistaking of particles 

 in an infusion which have heen there from the first for organisms 

 originated de novo, do not exhaust the list of conceivable explana- 

 tions of phenomena which have been attributed to spontaneous 

 generation. When the knowledge of the natural history of Bacteria 

 has advanced somewhat further, there will be a possibility of such 

 explanations presenting themselves in ways at this moment unsus- 

 pected. 



Whilst awaiting Professor Huizinga's fuller account of his 

 experiments, we may point out that the hypothesis of an inhibitory 

 influence of increased density should be supported by experimental 

 evidence, and that it cannot apply to tubes closed before boiling. 

 The neck of the flask closed with asphalt may (so far as conditions 

 are stated by him at jjresent) harbour Bacteria, as in our Series F. 

 But especially we would urge upon him and others that it is unde- 

 sirable, as yet, to introduce into the discussion other organic mix- 

 tures. Turnips and cheese may be very bad material for experi- 

 ment ; but it would be well, as far as possible, to settle the matter, 

 or the way in which the matter is to be viewed with regard to 

 them, before going off to other particular cases. 



It would be a very excellent thing if all further reference to 

 this subject could be postponed for a year or two — that is, until 

 further study of Bacteria, such as that inaugurated by Sanderson 

 and Cohn, has given us surer ground to tread upon. — Proceedings 

 of the Royal Society, No. 145. 



