But, with reference to these supposed cases of budding, and also to those others in which the contents of a spore or sporangium break up into what Professor Hallier calls “micrococci” (which are generally incipient Bacteria), it would be difficult for us to decide whether such processes are normal or abnormal. When we have to do with such organisms, in fact, there may be the nicest transitions between what is called Homogenesis, and what, when occurring in other organisms, we term Heterogenesis. It may be that the production of such “micrococci” from the spore or sporangium of the fungus is not an invariable incident in the life-history of the species, but rather an occasional result of the influence of unusual conditions, or of failing vigour on the part of the organism. In this latter case we should have to do with a process of Heterogenesis; although, as I have just stated, in respect to such low and changeable organisms, scarcely any distinct line of demarcation can be drawn between Homogenesis and Heterogenesis.
The evidence seems, therefore, against the notion that Bacteria or Torulæ are ordinary, independent living things, which merely reproduce their like.
That some Bacteria are produced from pre-existing Bacteria, just as some Torulæ are derived from pre-existing Torulæ, may, it is true, be considered as settled. But, so far as we have yet considered the subject, there may be just as good evidence to show that Bacteria and Torulæ are capable of arising de novo, as there is that some of them are capable of developing into fungi.
If this were the case, such types could only be regarded as the most common forms assumed by new-born specks of living matter; and, by reason of their origin – which would entail an absence of all hereditary predisposition – they might be supposed to be capable of assuming higher developmental forms.
Now, as a matter of fact, worthy of arresting our attention, we do find that some Bacteria are capable of growing into Leptothrix, whilst this is able to develop continuously into a fungus; just as we also know that some Torulæ are capable of growing into other fungi.
Should it be established, therefore, that Bacteria and Torulæ are capable of arising de novo, the facts concerning their mutability are harmonious enough with theoretical indications.
But, as I have before indicated, although it is quite true that some Bacteria develop into fungi, such forms may constitute no necessary links in the life-history of other fungi. I have suggested that in those (occasional) cases in which they do occur as links in the life-history of fungi, there is room for doubt whether these Bacteria are to be considered as normal products, or as abnormal results (heterogeneous offcasts), brought about by some unusual conditions acting upon the parent fungus. That is to say, we may be doubtful whether in such a case their origin ought to be considered Homogenetic or Heterogenetic. It may be that many of the lower fungi are such changeable organisms, and so prone to respond to the various “conditions” acting upon them (which would be almost certainly the case if they had been developed from a Bacterium in two or three days – the Bacterium itself having been evolved de novo) that no very valid distinction can here be drawn between Homogenesis and Heterogenesis. Our whole point of view, in fact, concerning such fungi as are seen to develop through Leptothrix forms from Bacteria must be entirely altered, if it is once conceded that Bacteria may arise de novo. Such simple Mucedineæ would then have to be regarded as mere upstart organisms only a few removes from dead matter, and – in view of the greater molecular mobility of living matter – capable of being modified in shape and form even more than the most changeable crystals under the influence of altering “conditions.” We should have no longer to do with the members of a stable species, which had been reproducing its like through countless geologic ages anterior to the advent of man upon the earth. Indeed, in order to reconcile such a possibility with the seemingly contradictory fact of the known extreme changeability of these lower forms of life, we hear only vague hints thrown out about our imperfect knowledge of the “limits within which species may vary.” As if, in the face of what we do know concerning hereditary transmission, this changeability did not make it almost impossible to conceive that there should have been an unbroken series of such organisms since that remote epoch of the earth’s history, when the first organisms of the kind made their appearance. It does not seem to me that the presumed permanence of a very changeable organism is consistent with, or rendered more explicable by, the supposition that some representatives of the species have constantly been undergoing progressive modifications which have been successively perpetuated by inheritance, in the shape of distinct specific forms. Why should some be presumed to have undergone so much change, whilst others (presenting an equal and an extreme degree of modifiability, even to the present day) are supposed to have preserved the same specific form through a countless series of changing influences?
2. Heterogenetic Mode of Origin of Bacteria and of Torulæ
It has been long known that Bacteria and Torulæ are frequently to be found within vegetable cells, taken even from the central parts of plants, whenever these are in a sickly condition or are actually dying. They are apt to exist also within epithelial cells taken from the inside of the mouth; and the frequency and abundance with which such organisms are met with in these cells, is almost in direct proportion to the malnutrition and lack of vital power in the individual who is the subject of observation. Then, again, in persons who have died of adynamic diseases, in the course of twenty-four or thirty-six hours (during warm weather) Bacteria may be found in abundance within the blood-vessels of the brain and of other parts, although no such Bacteria were recognizable in the blood of the individual during life.
In these cases we must, in order to account for the presence of the Bacteria and Torulæ, either suppose that such organisms, in an embryonic state, are almost universally disseminated throughout the various textures of higher organisms, both animal and vegetal (though they are only able to develop and manifest themselves when the higher organisms, or the parts of them in which the Bacteria or Torulæ are met with, are on the eve of death), or else we must imagine that when the vital activity of any organism, whether simple or complex, is on the wane, its constituent particles (being still portions of living matter) are capable of individualizing themselves, and of growing into the low organisms in question. Just as the life of one of the cells of a higher organism may continue for some time after the death of the organism itself, so, in accordance with this latter view, may one of the particles of such a cell be supposed to continue to live after even cell-life is impossible.
Now, to many persons, the latter seems to be a much simpler hypothesis than the former, and one, moreover, which is more in accordance with known facts. People’s views, however, on this subject are likely to be much influenced by their notions as to the possibility of Bacteria arising by a process of Archebiosis. Although some may be inclined to accept the doctrine of Heterogenesis, the same persons, being “vitalists,” may not readily believe in the doctrine of Archebiosis, because this implies the vivification of dead matter – the conversion of not-living elements into a living combination. Those, however, who do believe in Archebiosis will – if the necessary evidence be forthcoming