GENERAL OBSERVATIONS. 1035 



This view of the subordination of orgatiic evolution to general laws is 

 sustained by the paleontologist Professor A. Gaudry, of Paris, in his review 

 of the parallelism between Europe and America in the succession of types 

 from the Cambrian upward {Bull. Soc. Geol. de France, December, 1891). 

 He compares the correlate tribes through the successive stages of progress, 

 and the gradual changes by which old characteristics disappeared and new 

 features were developed for the two distant regions, notwithstanding the 

 differences that existed in climatal and other conditions ; and he concludes 

 that these and similar facts are not all explainable by migrations, but only 

 by evolution under general laws of progress. 



Origin of species. — The origin of the special causes for each line of 

 change or variation, which Darwin did not undertake to study out, is yet 

 very imperfectly understood. The paragraphs on the evolution of the Horse 

 and the Artiodactyl, on page 929, and others bearing in the same direction, 

 show some sixccess. It is admitted that (1) bones will coossify if movement 

 between them ceases ; (2) that the progressive enlargement of one organ or 

 part may cause the dwindling of others adjoining ; (3) that running under 

 an impulse would lead to a rising of the foot on the toes, to secure greater 

 length of lever and greater speed; (4) that activity in the limbs may deter- 

 mine adjustments in the position of the ankle bones fitted for greatest 

 strength and security ; (5) that the use of the teeth may lead to increased 

 complexity of structure. 



But from the statements with regard to the Horse and Artiodactyl, it 

 may be thought possible, also, that the great elongation of the foot, chiefly 

 of the metacarpals and metatarsals, would be a natural consequence of the 

 rhythmic stroke of the foot in running, this inducing a variation that Avas 

 continued in growth by interbreeding. And this apparent success in ex- 

 plaining leads to the suggestion that the graceful form, so general in fleet 

 animals, may be a result of the free movements of all parts of the structure 

 in running; and that the horns in the Ruminants and other Ungulates may 

 have come from a variation commenced by the strokes made by the forehead 

 or front of the head, in conflicts. 



But another Artiodactyl, the " high-reaching " Giraffe, puts a check to 

 speculation; for it has the anterior pair of legs much the longer, the foot 

 portion alone three feet long; and the neck more than triple the ordinary 

 length in Buminants, owing to the great elongation of six of the seven 

 vertebrae. The elongation of the legs has the same purpose as that of the 

 neck — "high-reaching in quest of food." The question conies up — How 

 should the Giraffe have had to run to make its fore legs grow faster than 

 the hind legs, and what kind of antics would have started the change in 

 the neck ? It has to be supposed that the requisite augmentative varia- 

 tions were somehow begun, and that under interbreeding, accelerated growth 

 went forward. But the origin of the variation is without explanation. 

 And so it is for the most part throughout the Kingdoms of life. Enough 

 is known to encourage study. 



