. Biology. Biology. HOMOLOGY AND ADAPTATION 185 II. GENERAL BIOLOGICAL INTEREST OF THE LOBSTER The structures and life history of the lobster teach, by anal- ogy, the story of evolution. Structural adaptations of animals to different modes of life, interpreted on the principle of homol- ogy, furnish evidence of the origin of species from generalized types. The appendages of the lobster are originally all alike, and of a primitive biramous type. From this primitive type by. FIG. 80.—A young lobster leaving the egg case (on left). (From Herrick.) various modifications, several different forms of
. Biology. Biology. HOMOLOGY AND ADAPTATION 185 II. GENERAL BIOLOGICAL INTEREST OF THE LOBSTER The structures and life history of the lobster teach, by anal- ogy, the story of evolution. Structural adaptations of animals to different modes of life, interpreted on the principle of homol- ogy, furnish evidence of the origin of species from generalized types. The appendages of the lobster are originally all alike, and of a primitive biramous type. From this primitive type by. FIG. 80.—A young lobster leaving the egg case (on left). (From Herrick.) various modifications, several different forms of the adult ap- pendages are derived. These appendages, furthermore, are utilized for different purposes, thus illustrating the principle of adaptation—a generalized type of organ may become adapted to several different kinds of uses. What happens among homologous parts in the individual lobster can, theoretically, take place in allied organisms of a given group, although the process cannot be watched as it can be in the lobster. We find, in existing animals, structural adaptations which we can interpret best on the theory of com- mon origin. Thus, in this one group of Crustacea to which the. 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 Calkins, Gary N. (Gary Nathan), b. 1869. New York, H. Holt and company
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