Sinopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 Excerpt: ...suck up the juices of flowers on which it now feeds. This is a typical case of abrupt metamorphosis, and it is obvious that the developmental history cannot here be a true recapitulation. It is quite impossible that the pupa, for instance, should ever have been an adult condition, and the abrupt character of the changes from caterpillar to pupa, and from pupa to imago, cannot be ancestral. Without entering at length into the origin of metamorphoses such as these, it may be pointed out that they only occur amongst insects, in forms in which the nature of the food, and therefore the structure of the jaws, is very different in the caterpillar and in the adult condition respectively; and that in such cases a gradual transition from one to the other would be quite impossible, for a mouth intermediate in its characters between the masticatory mouth of the caterpillar and the suctorial one of the butterfly would manifestly be incapable of either biting leaves or sucking the juices of flowers. In the case of other insects, such as the locust, cricket, or grasshopper, the developmental history is one of gradual progression, and not one of abrupt metamorphosis, each step being a step onwards towards the adult insect. In the cockroach, again, the process of development is gradual, and parts not present in the larva, such as the wings, appear not suddenly, but step by step and progressively. The differences in these cases between the young and the adult are not great. There is no doubt that gradual transformation is the simpler and more primitive condition, and that the action of Natural Selection may cause the larval and adult forms to move apart and constitute periods of growth and reproduction respectively. Natural Selection may also cause such specialisation of the...
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Reseña del editor
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1894 Excerpt: ...suck up the juices of flowers on which it now feeds. This is a typical case of abrupt metamorphosis, and it is obvious that the developmental history cannot here be a true recapitulation. It is quite impossible that the pupa, for instance, should ever have been an adult condition, and the abrupt character of the changes from caterpillar to pupa, and from pupa to imago, cannot be ancestral. Without entering at length into the origin of metamorphoses such as these, it may be pointed out that they only occur amongst insects, in forms in which the nature of the food, and therefore the structure of the jaws, is very different in the caterpillar and in the adult condition respectively; and that in such cases a gradual transition from one to the other would be quite impossible, for a mouth intermediate in its characters between the masticatory mouth of the caterpillar and the suctorial one of the butterfly would manifestly be incapable of either biting leaves or sucking the juices of flowers. In the case of other insects, such as the locust, cricket, or grasshopper, the developmental history is one of gradual progression, and not one of abrupt metamorphosis, each step being a step onwards towards the adult insect. In the cockroach, again, the process of development is gradual, and parts not present in the larva, such as the wings, appear not suddenly, but step by step and progressively. The differences in these cases between the young and the adult are not great. There is no doubt that gradual transformation is the simpler and more primitive condition, and that the action of Natural Selection may cause the larval and adult forms to move apart and constitute periods of growth and reproduction respectively. Natural Selection may also cause such specialisation of the...
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