credible that whilst all known forms of living matter with which accurate experiment has been made invariably perish at or below 140° F., the particular examples of some of the same forms which appear within our sealed flasks have been able to survive a much longer exposure to 270-275° F. If this were true, then indeed would the cultivation of Science be a vain pursuit-'uniformity,' in fact, must be postulated and granted, or Science with humbled and sorrowful crest must retire from the field.

A word or two may be said in conclusion with reference to the interpretation which should be attached to such experiments as those just recorded. And this subject cannot be better introduced than by means of the following extract from the alreadyquoted and valuable paper by Professor Jeffries Wyman.* He says:-" There can therefore be no certainty of the existence of spontaneous generation in a given solution, until it can be shown that this has been freed of all living organisms which it contained at the beginning of the experiment and kept free of all such from without during the progress of it. On the other hand, this kind of generation

* Whilst these pages have been passing through the press the sad news has reached us of the premature death of Professor Wyman. him Science has lost one of her most faithful followers.

In

becomes probable, whenever it is made certain that Infusoria are generated in solutions in which the conditions just mentioned have been complied with. We say probable, 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, as it appears to me, 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 halfrealised form in the minds of many distinguished persons. It is for this reason, and on account of the authority attaching to Professor 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, Hetero

genesis and Archebiosis.

With regard to Hetero

genesis, this is merely the opposite of Homogenesis ; and the latter is the name for that mode of generation or reproduction amongst 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 similar to 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 is therefore a truism to say that it can only take place where living matter pre-exists. And seeing that many investigators, amongst whom I may especially mention, Needham,* Pouchet, and Trécul, have, both now and formerly, understood by the phrase 'spontaneous generation,' merely such a process of metamorphosis of living matter as is implied by the term Heterogenesis, it is, to say the least, very misleading to assert without qualification that, "the absolute proof of spontaneous generation must come

* See "The Beginnings of Life," vol. i., pp. 246-252, and vol. ii., p. 181.

from the formation of living organisms out of inorganic matter."

It seems obvious, however, that when Professor Wyman wrote this passage, he, forgetting for the time the more common acceptation of the phrase 'spontaneous generation,' must have used it only in the sense in which I now employ the term Archebiosis-in the sense, that is, of life-origination. But, even taking the phrase 'spontaneous generation' in this one sense only, how far, we may ask, was Professor 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 consequently, if I am correct in this view, it should be professed by no consistent believer in Evolution. Those who do not assent to these physical doctrines of life would. probably never be able to believe in Archebiosis at all-to the 'vitalist,' life is an immaterial principle specially created, and therefore our flask experiments terminating in the birth of new organisms, could at the most be regarded by him as proving the occurrence of Heterogenesis. Life was there, he might say, as an indestructible principle, so that the new organisms which appear are simply new embodiments of this

'principle'-a kind of transformation has taken place. This, in short, is the view to which a vitalist would be driven, if he had become convinced that no germs of Bacteria, or of such other organisms as are found in our flasks, could have survived the preliminary process of heating. Such a vague sort of position is not open, however, to evolutionists or to those who believe in the now generally accepted physical doctrines of life. They are bound to recognize the undoubted distinction which exists between mere dead organic matter, and that organic matter which displays the phenomena of life. They should no more think of calling a body 'living' which could not be made to display the characteristics of life, than they would call a body 'magnetic,' when it would show none of the properties pertaining to magnetism. If they had learned, therefore, that living matter when exposed to heat of a certain intensity became lifeless matter (that is, that it could no longer be made to display the phenomena of life), the process by which new living protoplasm comes into existence amongst this dead organic material, would be, for them, as much an instance of its new independent origin as if the process had occurred in the midst of mere inorganic elements. The term Archebiosis is therefore applicable to the process that must take place in our ordinary flask