Lamarck, the Founder of Evolution: His Life and Work

by A. S. Packard

In an essay entitled “The Ancestry of Insects”[219] (1873) we adopted the Lamarckian factors of change of habits and environment, of use and disuse, to account for the origin of the appendages, while we attributed the origin of the metamorphoses of insects to change of habits or of the temperature of the seasons and of climates, particularly the change in the earth’s climates from the earlier ages of the globe, “when the temperature of the earth was nearly the same the world over, to the times of the present distribution of heat and cold in zones.”

From further studies on cave animals, published in 1877,[220] we wrote as follows:

“In the production of these cave species, the exceptional phenomena of darkness, want of sufficient food, and unvarying temperature, have been plainly enough veræ causæ. To say that the principle of natural selection accounts for the change of structure is no explanation of the phenomena; the phrase has to the mind of the writer no meaning in connection with the production of these cave forms, and has as little meaning in accounting for the origination of species and genera in general. Darwin’s phrase ‘natural selection,’ or Herbert Spencer’s term ‘survival of the fittest,’ expresses simply the final result, while the process of the origination of the new forms which have survived, or been selected by nature, is to be explained by the action of the physical environments of the animals coupled with inheritance-force. It has always appeared to the writer that the phrases quoted above have been misused to state the cause, when they simply express the result of the action of a chain of causes which we may, with Herbert Spencer, call the ‘environment’ of the organism undergoing modification; and thus a form of Lamarckianism, greatly modified by recent scientific discoveries, seems to meet most of the difficulties which arise in accounting for the origination of species and higher groups of organisms. Certainly ‘natural selection’ or the ‘survival of the fittest’ is not a vera causa, though the ‘struggle for existence’ may show us the causes which have led to the preservation of species, while changes in the environment of the organism may satisfactorily account for the original tendency to variation assumed by Mr. Darwin as the starting-point where natural selection begins to act.”

In our work on The Cave Animals of North America,[221] after stating that Darwin in his Origin of Species attributed the loss of eyes “wholly to disuse,” remarking (p. 142) that after the more or less perfect obliteration of the eyes, “natural selection will often have effected other changes, such as an increase in the length of the antennæ or palpi, as a compensation for blindness,” we then summed up as follows the causes of the production of cave faunæ in general:

“1. Change in environment from light, even partial, to twilight or total darkness, and involving diminution of food, and compensation for the loss of certain organs by the hypertrophy of others.

“2. Disuse of certain organs.

“3. Adaptation, enabling the more plastic forms to survive and perpetuate their stock.

“4. Isolation, preventing intercrossing with out-of-door forms, thus insuring the permanency of the new varieties, species, or genera.

“5. Heredity, operating to secure for the future the permanence of the newly originated forms as long as the physical conditions remain the same.

“Natural selection perhaps expresses the total result of the working of these five factors rather than being an efficient cause in itself, or at least constitutes the last term in a series of causes. Hence Lamarckism in a modern form, or as we have termed it, Neolamarckism, seems to us to be nearer the truth than Darwinism proper or natural selection.”[222]

In an attempt to apply Lamarck’s principle of the origin of the spines and horns of caterpillars and other insects as well as other animals to the result of external stimuli,[223] we had not then read what he says on the subject. (See p. 316.) Having, however, been led to examine into the matter, from the views held by recent observers, especially Henslow, and it appearing that Lamarck was substantially correct in supposing that the blood (his “fluids”) would flow to parts on the exposed portions of the body and thus cause the origin of horns, on the principle of the saying, “ubi irritatio, ibi affluxus,” we came to the following conclusions:

“The Lamarckian factors (1) change (both direct and indirect) in the milieu, (2) need, and (3) habit, and the now generally adopted principle that a change of function induces change in organs,[224] and in some or many cases actually induces the hypertrophy and specialization of what otherwise would be indifferent parts or organs;—these factors are all-important in the evolution of the colors, ornaments, and outgrowths from the cuticle of caterpillars.”

Our present views as to the relations between the Lamarckian factors and the Darwinian one of natural selection are shown by the following summary at the end of this essay.

“1. The more prominent tubercles, and spines or bristles arising from them, are hypertrophied piliferous warts, the warts, with the seta or hair which they bear, being common to all caterpillars.

“2. The hypertrophy or enlargement was probably [we should rather say possibly] primarily due to a change of station from herbs to trees, involving better air, a more equable temperature, perhaps a different and better food.

“3. The enlarged and specialized tubercles developed more rapidly on certain segments than on others, especially the more prominent segments, because the nutritive fluids would tend more freely to supply parts most exposed to external stimuli.

“4. The stimuli were in great part due to the visits of insects and birds, resulting in a mimicry of the spines and projections on the trees; the colors (lines and spots) were due to light or shade, with the general result of protective mimicry, or adaptation to tree-life.

“5. As the result of some unknown factor some of the hypodermic cells at the base of the spines became in certain forms specialized so as to secrete a poisonous fluid.

“6. After such primitive forms, members of different families, had become established on trees, a process of arboreal segregation or isolation would set in, and intercrossing with low-feeders would cease.

“7. Heredity, or the unknown factors of which heredity is the result, would go on uninterruptedly, the result being a succession of generations perfectly adapted to arboreal life.

“8. Finally the conservative agency of natural selection operates constantly, tending towards the preservation of the new varieties, species, and genera, and would not cease to act, in a given direction, so long as the environment remained the same.

“9. Thus in order to account for the origin of a species, genus, family, order, or even a class, the first steps, causing the origination of variations, were in the beginning due to the primary (direct and indirect) factors of evolution (Neolamarckism), and the final stages were due to the secondary factors, segregation and natural selection (Darwinism).”

From a late essay[225] we take the following extracts explaining our views: