The adaptation, however, of which there is question here is not to be confounded with the “acquired adaptation” of Lamarckian fame; for, unlike the latter, it is an inheritable modification rooted in the germ plasm. Adaptations of this sort do, indeed, adjust the organism to its external environment, but they are innate and not acquired. Hence they are often spoken of as preadaptations; for they precede, in a sense, the organism’s contact with the environing element to which they adjust it. They may possibly, it is true, have been acquired in the distant past, but they have now a specific germinal foundation, and no one was ever privileged to witness their initial production de novo. The whale, for example, though fundamentally a warm-blooded mammal, is superficially a fish, by reason of such a preadaptation to its marine environment. Preadaptation is of common occurrence, especially among parasites, symbiotes, commensals, and inquilines. Wasmann cites innumerable instances of beetles and flies so profoundly modified, in accommodation to their mode of life as guests in termite nests, that the systematist hesitates to classify them under any of the accepted orders of insects. Here the adaptive modification so disturbs the underlying homology as to make of these creatures taxonomical ambiguities. In the case of Termitomyia, he tells us, “the whole development of the individual has been so modified that it resembles that of a viviparous mammal rather than that of a fly.” (“The Problem of Evolution,” pp. 14, 15.)
Such modifications, however, amount to major, and not merely minor, differences. We are not dealing, therefore, with varietal distinctions here, but with specific, generic, and even ordinal differences. With reference to the phenomenon of adaptive modification,[3] three things, consequently, are worthy of note: (1) it has the semblance of being adventitious to the underlying structural uniformity; (2) it is of such magnitude that it cannot be ascribed to variation within the species; (3) it has been appropriated by the hereditary process, in the sense that it is now an “inherited” character based on the transmission of specific germinal factors.
Now it is claimed that for the occurrence of this kind of modification in conjunction with homology only one rational explanation is possible, and that explanation is evolution. If this contention be a sound one, and Dorlodot, who claims certitude for the evolutionary solution, insists that it is such, then, in the name of sheer logical consistency, but one course lies open to us. We cannot stop at Wasmann’s comma,[4] we must press on to the very end of the evolutionary sentence and sing with the choristers of Woods Hole:
“It’s a long way from Amphioxus,
It’s a long way to us;
It’s a long way from Amphioxus,
To the meanest human cuss.
Good-bye fins and gill slits;
Welcome skin and hair.
It’s a long, long way from Amphioxus,