able, because their appearance under such circumstances would not amount to a proof. The absolute proof of spontaneous generation must come from the formation of living organisms out of inorganic matter. If Infusoria are generated in solutions of organic matter, independently of spores or germs, the question may be fairly raised whether we do not begin the experiment with materials in which life already exists, even though this material is not in the form of distinct organisms." Now, these last few lines, as they at present stand, tend to convey to the reader very erroneous impressions, and yet I am aware that views of the same kind are very commonly expressed, and seem to exist in an inchoate or half-realized form in the minds of many distinguished persons. It is for this reason, and on account of the authority attaching to Prof. Wyman's statements, that I am induced to take notice of this particular passage in order to attempt its rectification.
In the first place, then, under the old term, "spontaneous generation," are included two processes quite distinct from one another—namely, Heterogenesis and Archebiosis. With regard to Heterogenesis, this is merely the opposite of Homogenesis: and the latter is the name for that mode of generation or reproduction among living things which is looked upon with most respect and which is most generally known. It is the process by which "like produces like," that is, where the offspring grow into beings like their parents. In Heterogenesis, on the other hand, we have the birth of dissimilar products, the beginning of a new branch from a "life-tree," in which the offspring have no tendency to assume the parental type. This occurs, for instance, where the protoplasmic matter of an animal or of a vegetal cell becomes modified and resolved into Bacteria. Here we have to do with the mere transformation of living matter. It can, therefore, only take place where living matter preexists. And seeing that many, among whom I may especially mention Needham,[1] Pouchet, and Trécul, have, both now and formerly, understood by the phrase spontaneous generation merely such a process of metamorphoses of living matter as is implied by the term Heterogenesis, it is very misleading to say that "the absolute proof of spontaneous generation must come from the formation of living organisms out of inorganic matter."
It seems obvious, however, that, when Prof. Wyman wrote this passage, he, forgetting the more common acceptation of the phrase "spontaneous generation," must have used it in the same sense as I now employ the term Archebiosis—in the sense, that is, of life-origination. But, even taking it in this sense, how far, we may ask, is Prof. Wyman justified in saying that its proof "must come from the formation of living organisms out of inorganic matter?"
The statement is, in my opinion, one which cannot be logically entertained by a believer in the ordinary physical doctrines of life, and
- ↑ See "The Beginnings of Life," vol. i., pp. 246-252, and vol. ii., p. 181.
