In these experiments with heated fluids in closed flasks, nothing is easier than to obtain negative results. The same kinds of infusions which--if care has been taken to obtain them strong enough--will in a few days teem with living organisms, often show no trace of living things after much longer periods, when the solutions are weak. Again, in those cases where only a few organisms exist in a solution which has been made the subject of experimentation, nothing is easier than by a perfunctory examination of the fluid to fail in finding any of these sparsely-distributed living organisms. Experiments, the results of which are positive, may, therefore, in the absence of sufficient care, be cited as negative; and experiments which would otherwise have been crowned with unmistakeably positive results, may be rendered wholly barren by the employment of infusions which have been carelessly made. A word of explanation seems necessary with regard to the introduction of the new term _Archebiosis_. I had originally, in unpublished writings, adopted the word _Biogenesis_ to express the same meaning--viz., life-origination or commencement. But in the mean time the word _Biogenesis_ has been made use of, quite independently, by a distinguished biologist, who wished to make it bear a totally different meaning. He also introduced the word _Abiogenesis_. I have been informed, however, on the best authority, that neither of these words can--with any regard to the language from which they are derived--be supposed to bear the meanings which have of late been publicly assigned to them. Wishing to avoid all needless confusion, I therefore renounced the use of the word _Biogenesis_, and being, for the reason just given, unable to adopt the other term, I was compelled to introduce a new word, in order to designate the process by which living matter is supposed to come into being, independently of pre-existing living matter. H. CHARLTON BASTIAN. _Queen Anne Street, W., May 8, 1871._ THE MODES OF ORIGIN OF LOWEST ORGANISMS. The mode of origin of _Bacteria_, and, to a less extent, of _Torulæ_, has been much discussed of late, and many different views have been advocated on this subject by successive writers.