Haeckel’s Villa at Jena.
It is a great work. How few there are in the whole of the nineteenth century that show the wealth of ideas we find in the first volume alone.[[4]] And this is only one volume. We have as yet said nothing of the idea that is of the greatest consequence in connection with Haeckel’s own development. He was a Darwinian from 1862 onwards. After 1866 and the publication of the General Morphology we find him dominated in all his work by one single idea from the Darwinian group. He brought this idea so effectively to the front, improved and developed it so assiduously, and applied it in so many ways, that it has come to be regarded as his own most characteristic work. It is inseparable from his name. Whatever the future may be, wherever Haeckel’s name is uttered people will add the phrase that was made peculiarly his after 1866, that colours and pervades all his works—technical, popular, polemical, or philosophical—as much as the word “Monism.” It is the phrase: the biogenetic law.
[4]. The reader may be interested to know that Haeckel gives a popular summary of his early work on individuality and on the mathematical types of organisms in a more recent work. This has been translated into English with the title The Wonders of Life. The two chapters that deal with these questions are omitted from the abridged cheap edition. [Trans.]
Here and there even in the first volume of the Morphology a note is struck that the reader cannot clearly understand. It increases in the second volume until it dominates the whole book.
The phrase is known far and wide to-day. This is partly due to Haeckel’s own insistence on it, but perhaps still more to the real value of the idea itself. It crops up in a hundred different fields—psychology, ethics, philosophy, even in art and æsthetics. I have been able to trace it even into modern mysticism. For the moment I will only point out that it has been attacked and misstated with real fanaticism, in spite of the splendid and perfectly clear account of it that Haeckel has given.
The proper place to read of it is, as I said, the second volume of the Morphology. This volume has to give an account of the evolution of organic forms. What is given rather casually, almost Socratically, in Darwin is now developed into a number of strict laws. This method of expounding more or less hypothetical, new, and insecure ideas in the form of laws has since been frequently attacked. Some have been led by it to take the ideas as so many dogmas, and even to learn the laws by heart as if they were texts in Scripture. Others have then laid the blame of this dogmatic interpretation on Haeckel himself. It is quite true that there was the possibility of a misunderstanding. People do not always think for themselves, and the statement of a proposition in the form of a law may prove a pitfall for them. The blind learning of them by heart is always mischievous. On the other hand, it might be urged that the statement of the ideas in this bald way affords the best opportunity for a thorough and rational criticism of them, precisely because they give such pregnant expression to the writer’s meaning. I do not find that order and strict logical definitions have ever done any harm of themselves, whatever it is that is put in order and defined. On the contrary. People must confuse order sometimes with real dogmatism. Of this there is not a word in the whole book, while at an important juncture the reader is actually warned to be on his guard against undue pressure. “In this,” we read in the twentieth chapter, “we do not wish to draw up a body of laws of organic morphology, but to give hints and suggestions for drawing them up. A science that is yet only in its cradle, like the morphology of organisms, will have many important changes to undergo before it can venture to claim for its general propositions the rank of absolute and unexceptionable natural laws.”
However that may be, it was in this provisional definition of laws that the famous biogenetic law first took shape, and with it a spirit entered into Darwinism in the narrower sense that was never again detached from its master, Haeckel.
Let us once more take a simple illustration from facts. Take a green aquatic frog and a fish, say a pike.
Both of them have a solid vertebral column in their frames, and therefore both must be classed amongst the vertebrates. But within the limits of this group they differ very considerably from each other. The frog has four well-developed legs, its body terminates in a tail, and it breathes by means of lungs, like a bird, a dog, or a human being. The fish has fins, it swims in the water by means of these fins and its long rudder-like tail, and it breathes the air contained in the water by means of gills. When we arrange the vertebrates in a series, with man at their head, it is perfectly clear that the frog stands higher than the fish in regard to its whole structure. It is lower than the lizard, the bird, or the mammal, but at the same time it is a little nearer to these three than the fish is. That was recognised long ago by Linné, who assigned them a corresponding rank. The fishes are the lowest group of the vertebrates; the frogs belong to the group immediately above them. Now let us see how one of these frogs is developed to-day. The frogs are oviparous (egg-laying) animals. The mother frog lays her eggs in the water, and in the ordinary course of nature a new little frog develops from each of these eggs. But the object that develops from them is altogether different from the adult frog.