A NEW THEORY OF THE ORIGIN OF SPECIES. 513 



terrestrial species, quadrupeds, and bipeds quite similar to birds, 

 except as to the faculty of liig-ht. By the variety of their types of 

 organization the}' form, as apth^ stated by Frederick A. Lucas, a sort 

 of epitome of the class of reptiles, ^ow, their appearance and differ- 

 entiation were comparatively abrupt and sudden phenomena. It does 

 not seem probable that they were formed b}^ the mechanism of natural 

 selection and that they were destroj'ed because of their inferiority to 

 other species in the struggle for existence. 



We arrive at similar conclusions from an examination of the first 

 placental mammals. The}^ appeared abruptly at the beginning of the 

 Tertiary period; they assumed a variety of forms almost as numerous 

 as those of the mammals of to-dav, and they finally disappeared. 



Besides the paleontologists, many' naturalists have pointed out the 

 existence, in animals of our own time, of abrupt variations that pro- 

 duce a new type that becomes fixed as soon as it appears, and that has 

 the value of a species distinct from that from which it was derived. 

 Mivart and Huxle}', Clos, Camerano, and Bateson have called atten- 

 tion to the existence of such discontinuous variations, which may afford 

 an explanation of the discontinuicy of species. Yet the g'reater num- 

 ber of the examples adduced b}^ these authors miiy be referred to the 

 category of monstrosities or teratogenic variations which have suc- 

 ceeded in becoming fixed. This is the case with species of Asterias 

 having numerous arms, with crinoids having three or four divisions, 

 with a certain number of levogyrate gastropods. However, abrupt 

 transformations have been noted by entomologists under perfectly 

 normal conditions. Standfuss, to whom we are indebted for some 

 extremely interesting experiments on the heredity in butterflies, 

 speaks of "explosive transformation," thus expressing the richness in 

 new forms suddenl}' produced from a single parent stock. 



III. 



The origin of the new theory of Hugo de Vries must be sought for in 

 this mass of observations, facts, and theoretical ideas relative to the 

 abrupt variation of species in opposition to the Darwinian idea of 

 slow variation. The Dutch naturalist has, in a manner, worked over 

 all these ideas and codified them into a coherent system. This system 

 already existed in embryo in the well-known little work which he 

 published in 1889 on intracellular pangenesis. His views were, at that 

 time, purely theoretical, for he had then only just begun his experi- 

 mental verifications. Since then, however, some of his experiments 

 have succeeded in an astonishing manner. To-day, therefore, it is the 

 views that have been scrutinized and verified which the celebrated 

 l)otanist presents to the scientific public in his work on the Theory of 

 Mutation, recently published at Leipzig, 



