ABSTRACT
The phylum Chordata includes three subphyla Cephalochordata, Urochordata and Vertebrata. The first two subphyla are collectively called Prochordata and belong to the primitive deuterostomes. The cephalochordates constitute the smallest chordate subphyla and comprise 35 species belonging to three genera: Branchiostoma, Epigonichthys and Asymmetron. Most lanceolates are gonochorics; however, anomalous occurrence of simultaneous hermaphroditic amphioxus species is reported. In gonochorics, sex ratio is male-biased, as in Branchiostomma lanceolatum. The two series of symmetric gonads are located ventrolaterally in Branchiostoma but Asymmetron develops gonads on only the right side of the body. The larvae are asymmetrical with the mouth on the left side and gills on the right side. On metamorphosis, bilateral symmetry is restored. Captive culture from egg to egg stage has been achieved only in B. belcheri. In temperate lanceolates, life span ranges from 2-3 years in B. floridae and B. belcheri to 8 years in B. Lanceolatu.
