56 



SCIENCE 



[Vol. LV, No. 1412 



of more liighly developed patriotism, most 

 teachers would keep for tliemselves and their 

 own students. At that time one morphological 

 laboratory was in purpose and aim very much 

 like another. Morphology was studied be- 

 cause it was the material believed to be most 

 favorable for the elucidation of the problems 

 of evolution, and we all thought that in em- 

 bryology the quintessence of morphological 

 trvith was most palpably presented. Therefore 

 everj' aspiring zoologist was an embryologist, 

 and the one topic of professional conversation 

 was evolution. It had been so in our Cam- 

 bridge school, and it was so at Hampton. 



I wonder if there is now a single place where 

 the academic problems of morphology which 

 we discussed with such avidity can now arouse 

 a moment's concern. There were of course 

 men who saw a little further, notably Brooks 

 himself. He was at that time writing a book 

 on hereditj', and, to me at least, the notion on 

 which he used to expatiate, that there was a 

 special physiology of heredity capable of in- 

 dependent study, came as a new idea. But no 

 organized attack on that problem was begun, 

 nor had any one an inkling of how to set about 

 it. So we went on talking about evolution. 

 That is barely 40 years ago; to-day we feel 

 silence to be the safer course. 



Systematists still discuss the limits of spe- 

 cific distinction in a spirit, which I fear is 

 often rather scholastic than progressive, but 

 in the other centers of biological research a 

 score of concrete and immediate problems have 

 replaced evolution. 



Discussions of evolution came to an end 

 primarily because it was obvious that no pro- 

 gress was being made. Morphology having 

 been explored in its minutest corners, we 

 turned elsewhere. Variation and heredity, the 

 two components of the evolutionary path, were 

 next tried. The geneticist is the successor of 

 the morphologist. We became geneticists in 

 the conviction that there at least must evolu- 

 tionary wisdom be found. We got on fast. 

 So soon as a critical study of variation was 

 amdertaken, evidence came in as to the way 

 in which varieties do actually arise in descent. 

 The unacceptable doctrine of the secular 



transformation of masses by the accumulation 

 of impalpable changes became not only unlike- 

 ly but gratuitous. An examination in. the 

 field of the interrelations of pairs of well 

 characterized but closely allied "species" next 

 proved, almost wherever such an inquiry could 

 be instituted, that neither could both have been 

 gradually evolved by natural selection from a 

 common intermediate progenitor, nor either 

 from the other by such a process. Scarcely 

 ever where such pairs co-exist in nature, or 

 occupy conterminous areas do we find an in- 

 termediate normal population as the theory de- 

 mands. The ignorance of common facts bear- 

 ing on this part of the inquiry which pre- 

 vailed among evolutionists, was, as one looks 

 back, astonishing and inexplicable. It had 

 been decreed that when varieties of a species 

 co-exist in nature, they must be connected 

 by aU intergradations, and it was an article 

 of faith of almost equal validity that the inter- 

 mediate form must be statistically the majority, 

 and the extremes comparatively rare. The 

 plant breeder might declare that he had vari- 

 eties of Primula or some other plant, lately 

 constituted, uniform in every varietal char- 

 acter breeding strictly true in those respects, 

 or the entomologist might state that a poly- 

 morphic species of a beetle or of a moth fell 

 obviously into definite types, but the evolu- 

 tionary philosopher knew better. To him such 

 statements merely showed that the reporter 

 was a bad observer, and not improbably a 

 destroyer of inconvenient material. Systema- 

 tists had sound information but no one con- 

 sulted them on such matters or eared to hear 

 what they might have to say. The evolution- 

 ist of the eighties was perfectly certain that 

 species were a figment of the systematist's 

 mind, not worthy of enlightened attention. 



Then came the Mendalian clue. We saw 

 the varieties arising. Segregation maintained 

 their identity. The discontinuity of variation 

 was recognized in abundance. Plenty of the 

 Mendelian combinations would in nature pass 

 the scrutiny of even an exacting systematist 

 and be given "specific rank." In the light of 

 such facts the origin of species was no doubt 

 a similar phenomenon. All was clear ahead. 



