Abstract
THE development of an animal from the zygote up to the adult condition is usually accompanied by a more or less regular and continuous increase in size. In the case of the Arthropoda, however, the enclosure of the body in a hard inextensible layer of chitin renders this impossible, and in accordance with this the chitinous exoskeleton is shed from time to time, each moult or ecdysis being followed by a rapid spurt of growth until the process is again blocked by the hardening of the new chitinous layer. In many of the better-known arthropods particular moults are associated with the attainment of particular stages of development—e.g. the penultimate and the last moult of a Lepidopterous insect—and the idea is very generally held that this applies to all ecdyses or moults in the Arthropoda. Consequently, when in the study of plankton it is found that specimens of the young of some particular crustacean fall into a large number of different types demarcated by slight differences in size and form, one very naturally regards these as forming typical successive stages of the life-history, the whole series being worked through by each developing individual.
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MACDONALD, R. Numerical Reduction of Instars in the Metamorphosis of Euphausids. Nature 117, 894 (1926). https://doi.org/10.1038/117894a0
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DOI: https://doi.org/10.1038/117894a0
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