By D. Williamson

Many organic evidence are irreconcilable with the idea that larvae and adults advanced from an analogous genetic inventory. the writer of this ebook attracts cognizance to those, and offers his replacement speculation that larvae were transferred from one taxon to another.

In his past e-book (Larvae and Evolution, 1992), the writer used larval move to provide an explanation for developmental anomalies in 8 animal phyla. within the current booklet, he claims that the elemental different types of all larvae and all embryos were transferred from international taxa. This results in a brand new, finished concept at the foundation of embryos and larvae, changing the discredited 'recapitulation' idea of Haeckel (1866). Metamorphosis, formerly unexplained, represents a metamorphosis in taxon in the course of development.

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Species of Dromia, for example, develop more thoracic exopods than the larvae of hermit crabs, but there has been a general evolutionary tendency in many groups of decapod crustaceans to reduce the number of thoracic exopods (Williamson, 1988b). The larval evidence is therefore consistent with the evolution of the Dromioidea from an ancestor that also gave rise to the Paguridae and the Diogenidae. This common ancestor was probably an early hermit crab, but it was much more evolved than the common ancestor of the Anomura and Brachyura.

Then if we look again at the adult, inside the calcareous shell we find an animal enclosed in a chitinous cuticle, with jointed limbs not unlike those of a shrimp, and, like a shrimp, it moults this cuticle at intervals and the body expands a little before the next cuticle hardens. So the evidence from the larva and the adult is fully compatible: a barnacle is a crustacean, not a mollusc. During the nineteenth century there was an increasing interest in the life histories of marine animals, but by the time The Origin of Species was published the number of accurate descriptions of reliably identified marine larvae was still quite small.

LARVAE AND EVOLUT ION 22 23 in accord. Most crustaceans, for example, hatch as either a nauplius or a zoea larva, and some hatch as a nauplius and later develop into a zoea. Both these types of larvae are limited to the Crustacea, and, like their corresponding adults, they can be identified to species and assigned to genera, families, and larger groups. The characters used in identifying and classifying larvae are, of course, different from those used in identifying and classifying adults, and in some cases the larvae are easier than the adults to identify and classify, whereas in other cases it is the other way round.

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