PRESENT TENDENCIES OF MORPHOLOGY 281 



first, the indestructibility of the past; second, the irreversibility of 

 evolution. 



It is there, we may say in passing, that all the difficulty of the 

 question of spontaneous generation or abiogenesis lies. If by a 

 miracle we should happen to produce from non-living material as 

 simple a living being as can be imagined, this new being would 

 certainly be different from all actually existing species, for the 

 latter have a past that the other would not have, and they bear in 

 their organism, which may be as rudimentary as we choose, traces 

 of all action to which their ancestors have been subjected. 



We may even infer that the hypothetical monads whose forma- 

 tion we might bring about by abiogenesis would differ from those 

 which have originated at other times by the same process. Besides 

 the fact that the environmental conditions in which they appeared 

 would necessarily be different, the complexes of organic materials 

 which would serve in their formation also would have their history, 

 and everything leads us to think that the properties of inanimate 

 bodies, as those of living beings, are to a certain extent functions 

 of their antecedents. 



Thus is explained why even to-day there exist very old living 

 forms which are not developed because they no longer have available 

 plastic potential, and which would perish before they would undergo 

 transformation. 



Thus is explained why it is vain to hope through special environ- 

 mental conditions to raise relatively inferior forms of life to a higher 

 level, and why it is useless to seek to modify physically or morally 

 in a desirable sense races which are considered rightly or wrongly 

 as relatively inferior, but in any case otherwise differentiated. Evo- 

 lution is not reversible, and we cannot by any process cause a living 

 being to return toward the point at which it was separated from 

 its original phylum in order to make it follow a different way from 

 that which it had at first taken. 1 



But the limits imposed upon our science by nature should not 

 hinder us from admiring its grandeur and from noting its prodigious 

 development. 



It is never necessary to doubt progress. It is almost thirty years 

 since, in the course of a lesson on the first phases of development of 

 the animal egg, I said, not without regret: "La Morphodynamique 



1 The generality of the pcecilogonic process shows the instability of evolution. 

 For according to Brillouin, irreversibility is introduced into rational mechanics 

 with instability. Irreversibility, which is the almost universal character of natural 

 phenomena realized in finite time, is by no means an objection to mechanical ex- 

 planation (mechanics of the nineteenth century or the more general mechanics 

 which caused us to discover electromagnetism) of the physical-chemical world. 

 Wherever we actually introduce it in order to come to an issue in a numerical 

 theory, of viscosity or of friction, a most profound analysis will cause the recog- 

 nition and study of the instability of molecular equilibrium. (Marcel Brillouin, 

 Notices sur ks travaux scientifiques, pp. 19-20, 1904.) 



