Viviparity in the halfbeak generaDermogenys andNomorhamphus (Teleostei: Hemiramphidae)

Gravid ovaries were examined histologically from two species of Nomorhamphus and 21 populations of Dermogenys. In addition, changes in dry-weight throughout gestation are provided for 15 populations. The ovaries are paired organs running along the lateral body wall and are separated along most of their length. In all specimens examined, embryos are fertilized within the ovarian follicle. Viviparity in these species is divided herein into five categories designated types I-V. In types I and II the entire gestation period is intrafollicular, whereas in types III-V only the early stages of gestation are intrafollicular with the major period of development occurring in the ovarian lumen (intraluminal). Type I is characterized by the retention of a large amount of yolk throughout gestation.…