oxygen and of silver begin to aggregate independently into crystals of oxide of silver; in a second increment of time the operation of the same causes produces similar results, only now part of the new crystalline matter forms in connection with the preëxisting germs of crystals, though part of it may still aggregate independently. During a third, a fourth, and in all succeeding increments of time, in which the same causes operate amid similar conditions, similar results must ensue. But, taking the process of origination which occurs in the first increment of time, would Prof. Tyndall have us believe that it is in any way different from that of growth which takes place in a second, third, or fourth increment of time? Does not the very fact that origination and growth so often occur simultaneously in the case of crystalline matter, and under the influence of the same causes, show us that the two processes are intrinsically similar, and that conditions favorable for growth are also likely to be favorable for origination? And if this be true for crystalline matter, may we not infer that it would also be true for living matter? These are questions neither asked nor answered in any definite manner by those whose opinions I have already cited. They are, however, questions by no means unworthy of an attentive consideration.
Although, as a general rule, conditions favorable for the growth of any particular kind of crystalline matter are likely to be favorable for its origination, still it must be acknowledged that the presence of a crystal will occasionally lead to its growth in a medium in which similar crystalline matter had previously shown no tendency to form independently—even in cases where the introduction of a non-crystalline nucleus would not be able to determine a similar formation of crystalline matter. In spite of the general law, therefore, that conditions favorable for the growth are also favorable for the origination of crystalline matter, we are compelled to admit that growth may be determined under certain conditions where origination does not occur, and that the presence of preëxisting crystalline matter favors the process. Now, a distinction of the same kind undoubtedly obtains in the case of living matter. We know, quite positively, that, although Bacteria will not originate in a previously-boiled ammonic tartrate solution, or "Pasteur's solution," the addition of a few of these organisms (all other conditions remaining the same) will soon occasion a very considerable growth of the living matter of which they are composed. We are thus reduced to ask whether the influence of the preëxisting nucleus is relatively more potent in the case of living matter than it is in the case of crystalline matter? This is a question which unfortunately we are unable definitely to answer. But, so long as we have no positive knowledge on this subject, we surely have little right to infer that processes both of origination and of growth continue in the case of crystalline matter, while the process of growth alone survives in the
- "The Beginnings of Life," vol. i., p. 325.