Arachnid and that there may be up to 600,000 in total. Arachnid Arachnids () are a class (Arachnida) of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Almost all adult arachnids have eight legs, although the front pair of legs in some species has converted to a sensory function, while in other species, different appendages can grow large enough to take on the appearance of extra pairs of legs. The term is derived from the Greek word ("aráchnē"), from the myth of the hubristic human weaver Arachne who was turned into a spider. Spiders are the largest order in the class,
History of Animals especially the wryneck, fishes and snakes. Book III The internal organs, including generative system, veins, sinews, bone etc. He moves on to the blood, bone marrow, milk including rennet and cheese, and semen. Book IV Animals without blood (invertebrates) – cephalopods, crustaceans, etc. In chapter 8, he describes the sense organs of animals. Chapter 10 considers sleep and whether it occurs in fish. Books V and VI Reproduction, spontaneous and sexual of marine invertebrates, birds, quadrupeds, snakes, fish, and terrestrial arthropods including ichneumon wasps, bees, ants, scorpions, spiders, and grasshoppers. Book VII Reproduction of man, including puberty, conception, pregnancy, lactation,