having two sexes, and they reproduce via external fertilization. They only reproduce during their spawning season, which varies slightly between species — usually corresponding to spring and summer months. All lancelets species spawn shortly after sunset, either synchronously (e.g. Branchiostoma floridae, about once every two weeks during spawning season) or asynchronously (Branchiostoma lanceolatum, gradual spawning through the season). Nicholas and Linda Holland were the first researchers to describe a method of obtaining amphioxus embryos by induction of spawning in captivity and in vitro fertilization. Spawning can be artificially induced in the lab by electric or thermal shock. History Taxonomy The first representative organism of the group to be described was Branchiostoma lanceolatum. It was described by Peter Simon Pallas in 1774 as molluscan slugs in the genus Limax. It was not until 1834 that Gabriel Costa brought the phylogenetic position of the group closer to the agnathan vertebrates (hagfish and lampreys), including it in the new genus Branchiostoma (from the Greek, branchio = "gills", stoma = "mouth"). In 1836, Yarrel renamed the genus as Amphioxus (from the Greek: "pointed on both sides"), now considered an obsolete synonym of the genus Branchiostoma. Today, the term "amphioxus" is still used as a common name for the Amphioxiformes, along with "lancelet," especially in the English language. The order Amphioxiformes was apparently named in 1886 in the Jahresbericht und Abhandlungen des Naturwissenschaftlichen Vereins in Magdeburg. Anatomy Observations of amphioxus anatomy began in the middle of the 19th century. First, the adult then the embryonic anatomy were described. Alexander Kowalevsky first described the key anatomical features of the adult amphioxus (hollow dorsal nerve tube, endostyle, segmented body, postanal tail). De Quatrefages first completely described the nervous system of amphioxus. Other important contributions to amphioxus adult anatomy were given by Heinrich Rathke and John Goodsir. Kowalevsky also released the first complete description of amphioxus embryos, while Schultze and Leuckart were the first to describe the larvae. Other important contributions to amphioxus embryonic anatomy were given by Hatschek, Conklin and later by Tung (experimental embryology). Anatomy Depending on the exact species involved, the maximum length of lancelets is typically . Branchiostoma belcheri and B. lanceolatum are among the largest. Except for the size, the species are very similar in general appearance, differing mainly in the number of myotomes and the pigmentation of their larvae. They have a translucent, somewhat fish-like body, but without any paired fins or