. Animal life as affected by the natural conditions of existence. Animal ecology. 340 THE INFLUENCE OF LIVING SUEEOUNDINGS. form of growth, otherwise determined by the pressure of the crab's abdomen, and we might expect to find that such false sym- metry would disappear, since the mechanical causes determining the gi-owth of the Pachybdella would no longer be able to act in the same way. This anticipation is not, however, justified; in the cut here given the abdomen of a crab is shown which bore on it three such uninvited guests, and although a certain irregularity is plainly perceptible in th
. Animal life as affected by the natural conditions of existence. Animal ecology. 340 THE INFLUENCE OF LIVING SUEEOUNDINGS. form of growth, otherwise determined by the pressure of the crab's abdomen, and we might expect to find that such false sym- metry would disappear, since the mechanical causes determining the gi-owth of the Pachybdella would no longer be able to act in the same way. This anticipation is not, however, justified; in the cut here given the abdomen of a crab is shown which bore on it three such uninvited guests, and although a certain irregularity is plainly perceptible in the form and dissimilarity of the three parasites, the false symmetry is quite normal and well developed in all three. This proves that in this case the false symmetry induced by pressure has already become an here-. Fio. 89.—A. apeoitaen of Carcinm manas, from Heligoland, with three parasitic specimens of Saaulina carcini. All three, in spite of their irregnlar growth, exhibit the false synmietry proper to the genus. ditary character of the species; otherwise it must have dis- appeared. Thus in this case, what was originally an abnormal and pathological character seems to have become a normal specific character, transmissible by inheritance. A still more wonderful instance of the same kind was long siQce described by Count Pourtal^s. During his dredging expedition in the "West Indies he discovered a horny coral (see fig. 90) invariably associated with an Annelid. The worm lives in a tube formed by the abnormal growth—which in this species has become normal— of the slender branches of the coral; they grow together into a rather fine network, and thus form. 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 Semper, C. (Carl), 1832-1893. New York, D. Appleton
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