4. Living matter (in the form of the specks above mentioned) does appear quickly and abundantly in ituations where the uniformity of natural phenomena entitles us to believe that no living matter (whether visible or invisible) could have pre-existed.

In support of the present occurrence of Heterogenesis.*

5. Actual observation with the microscope of many phenomena of this kind. (Vol. II., chaps. xvii., xix.-xxii.)

6. The analogy between the phenomena of Heterogenesis and those of Allotropism. (Vol. II., pp. 49-85.)

7. The fact that the presence of certain of the lowest organisms within higher organisms is more or less determinable at will. (Vol. II., pp. 317-345.)

8. Our power of determining the presence of animal or plantlike organisms at will, in vessels containing certain organic infusions. (Vol. II., pp. 209-219, 231-235.)

4. The occurrence of Life-Evolution or Archebiosis in certain experimental flasks is only to be denied by making another assumption (as to the power of resisting heat displayed by living matter), which is not only without scientific warrant, but is in opposition to established facts.

Against Panspermism and an exclusive belief in Homogenesis.

5. The gratuitous assumption that many otherwise good observers should all be deceivedsimply because their interpretations contradict the preconceived opinions of the majority of naturalists.

6. The absence of all reason why phenomena of Allotropism should not show themselves with different kinds of living matter, as with simpler molecular compounds.

7. The impossibility of explaining this, except by the disproved assumption that higher organisms are always permeated by innumerable invisible and generally latent germs of such lowest organisms.

8. Our power of watching all the stages by which these animal or plant-like forms are produced, from the "pellicle on hay infusions," and our inability otherwise to account for their first appear

* As most of these facts have not been referred to in this commuication, I subjoin, after each pair of paragraphs, references to the chapters or pages in which the subject has been discussed or referred to in my work, "The Beginnings of Life."

organization attained by the allotropic product, where a vegetal matrix is transformed into an animal organism.

16. The interchangeability of those organic forms which are derivable from originally similar vegetal matrices.

17. The extreme variability of the simplest representatives of the Vegetal Kingdom. (Vol. II., pp. 150-165, and Appendix D.)

18. The present existence amongst such lower organisms of all the gradations by which a purely sexual process of generation is gradually evolved. (Vol. II., p. 552, and Table.)

19. The explanation of the mysterious phenomena of "Alternate Generation" - and especially of the anomalous exceptions in the case of Medusa with large eggs.

20. The existence of multitudes of almost structureless organisms at the present day. (Vol. II., pp. 605–622.)

tions, by assuming them to be the faulty inferences of hasty or unskilled observers. (Vol. II., chaps. xx.xxii.)

16. Difficulties similar to those last-mentioned. (Vol. II., pp. 491-499.)

17. The impossibility of deny: ing the united but independent testimony of so many observers, although such variability seems irreconcilable with the notion of these organisms being direct continuations of an extremely ancient similar matter which has resisted change for ages.

18. The impossibility of finding any explanation of this fact which shall be consistent with an exclusive doctrine of Life-transmission and Homogenesis.

19. The absence of all explanation, not only of the phenomena but of the exceptions thereto. (Vol. II., pp. 560-571.)

20. The impossibility of believ ing that living matter could persist with so little change for 100,000,000 years or upwards, whilst other portions of the same matter have progressively developed into all the varied forms of Life that have appeared upon this globe.

Taken as a whole, the amount of evidence, both

deductive and inductive, seems, to say the least,

very decidedly to preponderate in favour of the present occurrence of Archebiosis and Heterogenesis. Both fact and reason appear to be notably insufficient on the side of the counter hypothesis. So that a careful consideration of the respective merits of the two views-looked at merely as hypotheses seems to show in a very unmistakable manner which is most worthy of our acceptance.

Whilst the hypothesis of Panspermism is based upon an illegitimate belief, is at variance with many uniformities of nature, and is wholly incapable of embracing the required facts, that of Archebiosis and Heterogenesis is legitimate in its foundation, is not at all at variance with natural uniformity, and is capable already of explaining a very wide circle of facts pertaining to the past and present history of our globe.

But these are the very tests by which we are accustomed to probe a new hypothesis, with the view of ascertaining its probable truth or falsity. What Mr. Justice Grove* said in 1866, when speaking of the Darwinian hypothesis, is now just as applicable concerning the hypothesis of the present occurrence of Archebiosis and Heterogenesis. He said :— "The fair question is, Does the newly proposed view remove more difficulties, require fewer assumptions,

* Presidential Address, in Report of British Association, 1866, p. xxviii.

and present more consistency with observed facts. than that which it seeks to supersede? if so, the philosopher will adopt it, and the world will follow the philosopher-after many days."

But if, even when looked at merely as hypotheses, that of Archebiosis with Heterogenesis seems so likely to drive the old doctrine out of the field, we instinctively look around us for one of those "crucial instances" which may serve, as has been so often the case in the history of science, finally to decide between the contending claims of old and new views.

Now a crucial instance of this kind (or opportunity of employing the all-decisive experimental "Method of Difference"), does very fortunately lie within our reach, and has already been referred to. Its true value, however, may be now more clearly seized by the reader; so that for this reason, and because all past discussions on the question of the Origin of Life have shown that this is the part of the subject whose scientific basis is least understood or most persistently disregarded, I venture, even though with some slight reiteration to make a few concluding remarks on this crucial test-whose decision the opponents of Archebiosis attempt to set aside by a mixture of what appears to me to be, illogical arguments and groundless assumptions.