. The advancement of science. Occasional essays & addresses. Natural history. 18 DEGENERATION : I the adult clog. The changes which have taken count- less ages in the one case, are accomplished in a few weeks in the other. And now we have to note the important fact which makes this process of development so intensely interesting in relation to the pedi- FiG 1 — In e-c. • a siuc^ie g^ec of the animal kingdom. There ^Xntif t-^ffra iB very strong reason to believe ^'°'^^ "• that it is a general law of trans- mission or inheritance, that structural characteristics appear in the growth of
. The advancement of science. Occasional essays & addresses. Natural history. 18 DEGENERATION : I the adult clog. The changes which have taken count- less ages in the one case, are accomplished in a few weeks in the other. And now we have to note the important fact which makes this process of development so intensely interesting in relation to the pedi- FiG 1 — In e-c. • a siuc^ie g^ec of the animal kingdom. There ^Xntif t-^ffra iB very strong reason to believe ^'°'^^ "• that it is a general law of trans- mission or inheritance, that structural characteristics appear in the growth of a young organism in the order in which those characteristics have been acquired by its ancestors. At first the egg of a dog represents (im^perfectly, it is true) in form and structure the earliest ancestors of the dog; a few days later it has the form and structure of somewhat later ancestors; later still the embryo dog resembles less remote ancestors ; until at last it reaches the degree of elaboration proper to its immediate forefathers. Accordingly the phases of development or growth of the young are a brief recapitulation of the phases of form through which the ancestors of the young creature have passed. In some animals this recapitulation is more, in others it is less complete. Sometimes the changes are hurried through and disguised, but we find here and there in these histories of growth from the egg most valuable assistance in the attempt to reconstruct the genealogical tree. The history of the development of the common frog is a good illustration of the hind of evidence in Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lankester, E. Ray (Edwin Ray), Sir, 1847-1929. London and New York, Macmillan
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
