686 REVIEWS AND BOOK NOTICES. 
in respect to the prevalent methods of investigating questions of 
‘¢spontaneous generation.” Dissatisfied, as most thinkers are, 
with the vague and uncertain methods and conclusions of heated 
infusions and sealed flasks, the authors turned for an answer to 
the life history of the individual monads, and fortunately succeeded 
in obtaining the history of a species which might easily have been 
described as a group of species or quoted as an organism of spon- 
taneous origin. 
The necessity for a change in the methods of study in biogen- 
esis is well stated in their words, as follows :—‘*The question as to 
whether vital forms of the lowliest and minutest kind may have 
their origin in a new, and as yet unexplained, arrangement of 
non-vital material, is one that can never find a legitimate and final 
reply in the class of experiments employed to test it within the 
last thirty years. A careful student of the literature of the 
subject will see that the results obtained by the same and different 
experimenters, with similar infusions and solutions, are so un- 
certain, and often contradictory, as to leave the whole question 
open to bias; and an almost equal array of so-called ‘ experi- 
mental facts’ from nearly equally trustworthy observers, may be 
quoted on either side. This may be all pleasant enough in & 
‘wordy war, but it does not even approximate to a decision of 
the issue, and points to insufficiency in the experiments employed. 
The appearance or non-appearance of organic forms in certain 
infusions placed in sealed flasks or tubes, or otherwise conditioned, 
is held to be decisive of their production de novo or otherwise; 
but in point of fact we know nothing — absolutely nothing —of the 
life history of the greater number of the forms produced. To 
attempt to decide, therefore, from the experiments as yet pub- 
lished, that their production in gross masses in inorganic infusions 
proves that inorganic eléments produced them, may be to beg the 
whole question. Inferring from what we know of nature’s modes 
of reproduction, we have a right to expect, not a de novo produc- 
tion, but a production from genetic elements. But when we re- 
member the relation in size, throughout nature, between the ova 
and spermatozoa and the organism producing them, the fact that 
no such elements are visible (if they exist) in Bacteria or monads 
is probably a mere necessity of our present instrumental power. 
At least this is inevitable, that before we can be scientifically 
certain that these:lowly forms do or do not originate in non-y! 
