Hermit crab crab has several long spines, a long, narrow abdomen, and large fringed antennae. Several zoeal moults are followed by the final larval stage, the megalopa. Hermit crabs are often seen as a "throwaway pet" that would live only a few months, but species such as "Coenobita clypeatus" have a 23-year lifespan if properly treated, and some have lived longer than 32 years. Hermit crabs are more closely related to squat lobsters and porcelain crabs than they are to true crabs (Brachyura). However, the relationship of king crabs to the rest of Paguroidea is a highly contentious topic. Many studies based
On the Origin of Species an incipient species" and that "species are only strongly marked and permanent varieties". He argues for the ubiquity of variation in nature. Historians have noted that naturalists had long been aware that the individuals of a species differed from one another, but had generally considered such variations to be limited and unimportant deviations from the archetype of each species, that archetype being a fixed ideal in the mind of God. Darwin and Wallace made variation among individuals of the same species central to understanding the natural world. In Chapter III, Darwin asks how varieties "which I have called incipient species"