The sketch of 1844 is written in a clerk's hand, in two hundred and thirty-one pages folio, blank leaves being alternated with the MS. with a view to amplification. The text has been revised and corrected, criticisms being pencilled by himself on the margin. It is divided into two parts: I. "On the variation of Organic Beings under Domestication and in their Natural State." II. "On the Evidence favourable and opposed to the view that Species are naturally formed races descended from common Stocks." The first part contains the main argument of the 'Origin of Species.' It is founded, as is the argument of that work, on the study of domestic animals, and both the Sketch and the 'Origin' open with a chapter on variation under domestication and on artificial selection. This is followed, in both essays, by discussions on variation under nature, on natural selection, and on the struggle for life. Here, any close resemblance between the two essays with regard to arrangement ceases. Chapter III. of the Sketch, which concludes the first part, treats of the variations which occur in the instincts and habits of animals, and thus corresponds to some extent with Chapter VII. of the 'Origin' (1st edition). It thus forms a complement to the chapters which deal with variation in structure. It seems to have been placed thus early in the Essay to prevent the hasty rejection of the whole theory by a reader to whom the idea of natural selection acting on instincts might seem impossible. This is the more probable, as the Chapter on Instinct in the 'Origin' is specially mentioned (Introduction, page 5)as one of the "most apparent and gravest difficulties on the theory."Moreover the chapter in the Sketch ends with a discussion, "whether any particular corporeal structures...are so wonderful as to justify the rejection prima facie of our theory." Under this heading comes the discussion of the eye, which in the 'Origin' finds its place in Chapter VI. under "Difficulties of the Theory." The second part seems to have been planned in accordance with his favourite point of view with regard to his theory. This is briefly given in a letter to Dr. Asa Gray, November 11th, 1859: "I cannot possibly believe that a false theory would explain so many classes of facts, as I think it certainly does explain. On these grounds Idrop my anchor, and believe that the difficulties will slowly disappear."On this principle, having stated the theory in the first part, he proceeds to show to what extent various wide series of facts can be explained by its means.
Thus the second part of the Sketch corresponds roughly to the nine concluding Chapters of the First Edition of the 'Origin.' But we must exclude Chapter VII. ('Origin') on Instinct, which forms a chapter in the first part of the Sketch, and Chapter VIII. ('Origin') on Hybridism, a subject treated in the Sketch with 'Variation under Nature' in the first part.
The following list of the chapters of the second part of the Sketch will illustrate their correspondence with the final chapters of the 'Origin.'
Chapter I. "On the kind of intermediateness necessary, and the number of such intermediate forms." This includes a geological discussion, and corresponds to parts of Chapters VI. and IX. of the 'Origin.'
Chapter II. "The gradual appearance and disappearance of organic beings."Corresponds to Chapter X. of the 'Origin.'
Chapter III. "Geographical Distribution." Corresponds to Chapters XI. and XII. of the 'Origin.'
Chapter IV. "Affinities and Classification of Organic beings."Chapter V. "Unity of Type," Morphology, Embryology.
Chapter VI. Rudimentary Organs.
These three chapters correspond to Chapter XII. of the 'Origin.'
Chapter VII. Recapitulation and Conclusion. The final sentence of the Sketch, which we saw in its first rough form in the Note Book of 1837, closely resembles the final sentence of the 'Origin,' much of it being identical. The 'Origin' is not divided into two "Parts," but we see traces of such a division having been present in the writer's mind, in this resemblance between the second part of the Sketch and the final chapters of the 'Origin.' That he should speak ('Origin,' Introduction, page 5.) of the chapters on transition, on instinct, on hybridism, and on the geological record, as forming a group, may be due to the division of his early MS. into two parts.
Mr. Huxley, who was good enough to read the Sketch at my request, while remarking that the "main lines of argument," and the illustrations employed are the same, points out that in the 1844 Essay, "much more weight is attached to the influence of external conditions in producing variation, and to the inheritance of acquired habits than in the Origin.'"It is extremely interesting to find in the Sketch the first mention of principles familiar to us in the 'Origin of Species.' Foremost among these may be mentioned the principle of Sexual Selection, which is clearly enunciated. The important form of selection known as "unconscious," is also given. Here also occurs a statement of the law that peculiarities tend to appear in the offspring at an age corresponding to that at which they occurred in the parent.
Professor Newton, who was so kind as to look through the 1844 Sketch, tells me that my father's remarks on the migration of birds, incidentally given in more than one passage, show that he had anticipated the views of some later writers.
With regard to the general style of the Sketch, it is not to be expected that it should have all the characteristics of the 'Origin,' and we do not, in fact, find that balance and control, that concentration and grasp, which are so striking in the work of 1859.
