The Theory of Evolution:
With special reference to the evidence upon which it is founded (1917) pp. 37-41
William Berryman Scott

Even under conditions which cannot be called domestication, certain remarkable transformations of animals have been observed. An interesting case of this sort is that of the Porto Santo Rabbit, as described by Darwin. At a date variously given as 1418,1419 and 1420, the Portuguese navigator Zarco set free a doe and newly born litter of young rabbits upon the small island of Porto Santo, not far from Madeira. From the fact that the doe littered on shipboard, it is evident that she belonged to one of the domestic races, all of which have been derived from the European wild Rabbit (Lepus cuniculus). The absence of any carnivorous creatures, which would have preyed upon the rabbits, or of any other land mammal, which might have competed with them for food, led to a very rapid multiplication, so that in less than 40 years they are described as "innumerable." As a result of four and a half centuries of isolation under these novel conditions, the Porto Santo Rabbit has become so different from any of the domestic races and from its wild progenitor, that Haeckel has described it as a distinct species, Lepus huxleyi. The new form is much smaller than the European wild Rabbit, weighing but little more than half as much as the latter, and differs considerably in colour. The fur is redder, with far fewer black-tipped hairs; the throat and belly are gray or lead-coloured, instead of pure white, and the tips of the ears and upper surface of the tail lack the blackish-gray fur so characteristic of the European wild form.

"The two little Porto Santo rabbits, whilst alive in the Zoological Gardens, had a remarkably different appearance from the common kind. They were extraordinarily wild and active, so that many persons exclaimed on seeing them that they were more like large rats than rabbits. They were nocturnal to an unusual degree in their habits, and their wildness was never in the least subdued. … Lastly, and this is a highly remarkable fact, Mr. Bartlett could never succeed in getting these two rabbits, which were both males, to associate or breed with the females of several breeds which were repeatedly placed with them.

1 Darwin, Variation of Animals and Plants
under Domestication, Vol. I, pp. 119-20.

"If the history of these Porto Santo rabbits had not been known, most naturalists, on observing their much reduced size, their colour, reddish above and gray beneath, their tails and ears not tipped with black, would have ranked them as a distinct species. They would have been strongly confirmed in this view by seeing them alive in the Zoological Gardens, and hearing that they refused to couple with other rabbits. Yet this rabbit, which there can be little doubt would thus have been ranked as a distinct species, has certainly originated since the year 1420. Finally, from the three cases of the rabbits which have run wild in Porto Santo, Jamaica, and the Falkland Islands, we see that these animals do not, under new conditions of life, revert to or retain their aboriginal character, as is so generally asserted to be the case by most authors."1

Another instance of transformation, in this case very rapid, under "new conditions of life" is that of the Lunar Moth (Saturnia luna) when transported from Texas to Switzerland. In the year 1870, the entomologist Boll brought to Switzerland a number of cocoons of this large and beautiful moth and in May of the following year the full-grown moths emerged from the cocoons and differed in no particular from the ordinary Texas form. From these moths several hundred fertilized eggs were obtained, from which, in the course of a few weeks, small caterpillars were hatched. In Texas the caterpillars of this species feed upon the leaves of hickory and black walnut trees, but, as such leaves were not to be had in Switzerland, those of the European walnut were substituted. The substitution was entirely acceptable to the caterpillars, which ate greedily and formed their cocoons at the end of June, the adult moths emerging early in August. Much to the surprise of all observers, this second generation of moths, the caterpillars of which were fed upon a plant new to them, differed so much in form, colour and markings from the parent Texan species, that any entomologist would have regarded it as a new and distinct species, had its origin not been known. Nevertheless, Dr. Gemminger, a distinguished entomologist, recognized it as a distinct species and named it "Saturnia bolli."

Moritz Wagner, from whom this account is taken, gives the following description of the new form: "At the first glance, the connoisseur is surprised by the striking change of form. In the new species the shape of the body, as of the wings, is somewhat larger and heavier, while the feathery antennae are slightly narrower and less luxuriant. From the longer hind-body of the new species the carmine-red, longitudinal stripes, which the parent species bears, have completely disappeared. The front wings have a less sinuous form, but are somewhat broader. This change of form is to be more decidedly observed in the tail-like prolongation of the hind wings. Not less striking than the differences of shape are those of colour. In the ancestral species the colour is a yellowish green, while that of the new species is a beautiful lemon-yellow. The carmine-red marginal stripe, with whitish inner border, borne on the anterior wings of Saturnia luna, has quite disappeared in Saturnia bolli and is indicated only by a very narrow, dark yellowish colouring of the outermost margin.

1 M. Wagner: Die Entstehung der Arten
durch räumliche Sonderung, pp. 309-10.

"Most remarkable in this new species is the appearance of a new marking on the anterior wings, which appears as a transverse stripe, with somewhat zig-zag outer edge, but is entirely absent from the anterior wings of the parent species."1

Other similar, if less striking, examples of change might be described, did time permit; all that can be attempted here is to give an outline sketch of the evidence with a few illustrations, chosen from the many that are available. To present anything like an exhaustive display of the evidence would require, not one course of lectures, but many. The instances selected suffice to show that, when placed under new conditions of climate, food-supply, attacks of enemies and the like, animals and plants, whether domesticated or free, may experience very marked changes of size, form and appearance and that species are, in very many cases, if not in all, far from immutable. Often the metamorphosis is so great, that the wild progenitor of many domesticated animals and cultivated plants cannot be determined with any degree of certainty.

The other lines of evidence which are relied upon to prove the theory of evolution are comparative anatomy; embryology, the study of individual development; palaeontology, the study of extinct plants and animals which formerly existed on the earth; the geographical distribution of organisms, animal and vegetable; finally, experimental investigation. Each one of these methods of research has its particular advantages, as well as its special limitations and drawbacks; it is the harmonious result of all of them, pointing in the same direction, which gives great weight to their combined testimony.


Jethro Tull (1751):
So Silkworms, hatch'd and bred in France, of Eggs or Seed brought from Italy, will make as fine Silk as the Italian; but the Eggs of these laid in France, and their Issue, will make no better Silk than the French; though their Food be from Leaves of the same Mulberry-trees, when they make fine Silk and coarse: Therefore 'tis from the Climate, where the Eggs are impregnated, not where they have their Incubation or Food when hatch'd, and fed to their Lives End, that this Difference happens.