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such a gradual process, were not intergradations more common? Why 
did most of the supposed intergradations prove to be rare and partially 
sterile hybrids? Why, if evolution were still going on, could one 
recognize speciation at all in some of the groups? To the theoretical 
evolutionist, who knew as little as possible about species, such questions 
indicated merely the perversity of the systematist. The latter, 
accepting the general truth of evolution, but influenced hardly at all 
in his attitude by the manner in which it was supposed to have taken 
place, continued to describe species and then still more species, just as he 
had always done, and just as he will doubtless continue to do. Some- 
times he told what he thought about their relationships, oftener he 
did not, but he seldom failed to add to his description some variation 
of the formula "entirely distinct from its nearest ally." He has been 
anathematized; some of his colleagues have even threatened to cast 
him into outer darkness. Nevertheless, his work has certainly been 
as truthful and as serviceable as the work of those who deplore his 
"raking together of straws and sticks and even antique dust." 
It will require the combined efforts of morphologist, systematist, 
and geneticist to arrive at the whole truth in regard to genetic relation- 
ships. In one way the geneticist has a great advantage over the other 
workers, for his methods are inductive, whereas theirs are deductive. 
In another way he is at a great disadvantage, for he can deal only with 
the lesser categories, the variety, the species and perhaps the genus. 
The relationship of the larger groups must be determined, if at all, 
by the deductive methods of the morphologist, and, I may add, of the 
biochemist; for, as the years go on, biochemistry will come to be appHed 
more and more to the elucidation of genetical problems. 
The immediate aims of the geneticist are (i) to observe the origin 
of new and distinct forms, the genetic relationship of which must, 
therefore, of necessity be known, (2) to determine the conditions which 
brought these forms about, and (3) to study their hereditary behavior 
and their morphological and chemical characteristics in order to provide 
a basis for sound deduction in regard to multitudes of types which we 
can never hope to know except as facts of nature. All three aims have 
already been realized in some measure as a result of the recent activity 
in genetics. 
Most of the new forms of which the origin has been observed, 
belong to one class of organisms — namely, recessive Mendelian 
varieties. Such varieties have been observed to originate in two ways, 
