508 A NEW THEORY OF THE ORIGIN OF SPECIES. 



the illustrious English naturalist who first explained the mechanism 

 by which, according" to him, the transformation of one species into 

 another might be etfected, thus producing a continuity of living forms. 

 This mechanism is natural selection. 



Now it appears that, while Darwin succeeded in establishing the 

 idea of the continuity of living forms by means of generation — that is to 

 sa}". transformism, he was much less successful as regards the means 

 which ho proposed. To speak plainl}', he failed. There'are but few 

 naturalists at the present time who attribute to natural selection any 

 role whatever in the filiation of species. As has been remarked by 

 Herbert Spencer, it is not in this way that truly specific characters 

 can be acquired. Besides, when once acquired, the}' coidd certainly 

 not be fixed by heredity. It is some ten years since an3'one has held 

 to the fixed hereditv of characters acquired by a living being in the 

 course of its existence, or at least during ten years past that idea, 

 formerly admitted without opposition, has been fiercely attacked and 

 denied by naturalists of great standing, sucli as Weismann, Pfiiiger, 

 Naegeli, Strasburger, Kolliker, His, Kay-Lankester, Brooks, Meynert, 

 van Bemmelen, and others. 



A Dutch naturalist, Hugo de Vries, who has a wide reputation 

 among the botanists of our time, has just given the finishing stroke to 

 the theory of natural selection, already much shaken, and has pro- 

 posed in place of it another hypothesis which he calls ''the theory of 

 mutation." The name in itself is not very significative and needs to 

 be explained. We shall do that presently. The doctrine is founded 

 on ol)servation and experiments which by the sagacity, long and 

 patient effort, and careful criticism of their author deserve to be ranked 

 with the admirable o})servations of Darwin. On the other hand, it 

 has been most favorably received by many naturalists. For these two 

 reasons the scientific public is obliged to take it into consideration, 

 and. at least, to become acquainted with it. 



I. 



Every new being resembles the ones from which it ascended, con- 

 sidering those in the widest sense. We say — and it is only a form of 

 speech — that it owes this resemblance to heredity. Heredit}^ then, is 

 simply the name by which we express the fact that an ofi'spring 

 resembles its parents. On the other hand, the resemblance is not 

 absolute. For example, two animals of the same litter or two plants 

 of the same sowing are never identical. We apply the term " varia- 

 tion,''' individual variation, to such divergences or to the tendency 

 which produces them. It is, then, a fact that in new generations there 

 appear new characters which it is impossible to attribute to a reversion 

 to ancestral features — that is to say. they are truly new and unde- 

 scribed hitherto. It is only as to the extent and importance of such 

 characters that discussion arises. 



