HEEEDITY BATESON. 365 



may be taken to indicate that segregation can happen at earlier 

 stages of differentiation. 



The paradoxical descent of color blindness and other sex-limited 

 conditions, formerly regarded as an inscrutable caprice of nature, 

 has been represented with approximate correctness, and we already 

 know something as to the way, or, perhaps, I should say ways, in 

 which the determination of sex is accomplished in some of the forms 

 of life, though, I hasten to add, we have no inkling as to any method 

 by which that determination may be influenced or directed. It is 

 obvious that such discoveries have bearings on most of the problems, 

 whether theoretical or practical, in which animals and plants are 

 concerned. Permanence or change of type, perfection of type, 

 purity or mixture of race, " racial development," the succession of 

 forms, from being vague phrases expressing matters of degree, are 

 now seen to be capable of acquiring physiological meanings, already 

 to some extent assigned with precision. For the naturalist — and it 

 is to him that I am especially addressing myself to-day — these 

 things are chiefly significant as relating to the history of organic 

 beings — the theory of evolution, to use our modern name. They 

 have, as I shall endeavor to show in my second address to be given 

 in Sj^dne}^, an immediate reference to the conduct of human societ3^ 



I suppose that everyone is familiar in outline with the theory of 

 the origin of species which Darwin promulgated. Through the last 

 50 years this theme of the natural selection of favored races has been 

 developed and expounded in writings innumerable. Favored races 

 certainly can replace others. The argument is sound, but we are 

 doubtful of its value. For us that debate stands adjourned. We go 

 to Darwin for his incomparable collection of facts. We would fain 

 emulate his scholarship, his width, and his power of exposition, but 

 to us he speaks no more with philosophical authority. We read his 

 scheme of evolution as we would those of Lucretius or of Lamarck, 

 delighting in their simplicity and their courage. The practical and 

 experimental study of variation and heredity has not merely opened 

 a new field; it has given a new point of view and new standards of 

 criticism. Naturalists may still be found expounding teleological 

 systems^ which would have delighted Dr. Pangloss himself, but at 



I I take the following from the abstract of a recent Croonian lecture " On the Origin 

 of Mammals " delivered to the Royal Society : " In Upper Triassic times the larger 

 Cynodonts preyed upon the large Anomodont, Kannemeyeria, and carried on their ex- 

 istence so long as these Anomodonts survived, but died out with them about the end of 

 the TFias or in Rhaetic times. The small Cynodonts, having neither small Anomodonts 

 nor small Cotylosaurs to feed on, were forced to hunt the very active long-limbed Theco- 

 donts. The greatly increased activity brought about that series of changes which formed 

 the mammals — the flexible skin with hair, the four-chambered heart and warm blood, the 

 loose jaw with teeth for mastication, an increased development of tactile sensation and 

 a great increase of cerebrum. Not improbably the attacks of the newly-evolved Cynodont 

 or mammalian type brought about a corresponding evolution in the Psuedosuchian Theco- 

 donts which ultimately resulted in the formation of Dinosaurs and Birds." Broom, R., 

 Proc. Roy. Soc. B., 87, p. 88. 



