Twenty-three stages in the embryonic development of the western painted turtle, Chrysemys pictu bellii are described. The staging is based primarily on morphological changes, as well as age and size of the embryo. This is the first complete series showing the embryonic development of an emydid turtle. It documents the external changes of the embryo of Chrysemys picta bellii throughout its development. Yntema ('68) described in detail, the embryonic development of the snapping turtle, Chelydra serpentina. Pasteels ('57) studied gastrulation in three genera of turtles, C l e m m y s , C h r y s e m y s , and Pseudemys but did not describe later stages.Since extensive studies of the development of the extraembryonic membranes in turtles have already been published by Mitsukuri ( C l e m m y s , T r i o n y x , l89l), Mehnert ( E m y s , 1895), and Fisk and Tribe ( C h r y s e m y s and Chelydra, '49), they are but briefly treated here. METHODSA total of one-hundred and five western painted turtles ( C h r y s e m y s picta bellii) with mature eggs were collected over a two year period from Central Wisconsin during the laying season (late May to midJune). The turtles were either collected from shallow waters or captured when they were searching for nesting sites and brought to the laboratory to be sacrificed immediately. Eggs (675) were removed from the oviducts, washed with distilled water and incubated in flower pots containing damp sand at a depth of five inches. The pots were kept in a green house at a temperature ranging between 21 and 2 3°C . A total of 446 eggs out of the original 675 incubated showed development.Throughout the period of incubation, four embryos from different clutches were opened daily for the staging study. The time intervals between stages varied from one day during the first eight stages to several days thereafter. The embryos were staged primarily by morphological changes, however, chronological age and size of the embryo was also taken into consideration. As morphological features became prominent they were used as criteria for staging. The first four stages (pre-somite stages) were determined by changes in the shape of the blastopore and the development of the notochord, the neural folds and the head folds. Stages 5 to 10 were defined primarily on the number of somites and the development of the brain, the heart and the gill arches. Other stages were defined on the basis of limb and shell formations.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Society for the Study of Amphibians and Reptiles is collaborating with JSTOR to digitize, preserve and extend access to Journal of Herpetology. ABSTRACT-Male and female reproductive cycles were studied in 4 species of kinosternid turtles (Kinosternon subrubrum hippocrepis, K. f. flavescens, Sternotherus odoratus, and S. carinatus) collected from Arkansas, Texas, and Oklahoma. Spermatogenesis begins in June and reaches a peak by mid-August when the testes attain maximum size. Testicular regression begins shortly after the cessation of spermatogenesis. Follicular growth began during late summer but did not reach its peak until the following spring just prior to ovulation. Egg-laying is usually from May to early June. Regression of corpora lutea is complete in about 3 months. There was no correlation between body size and egg clutch size or testes weight. * * * (Kinosternon flavescens flavescens), the common musk turtle (Sternotherus odoratus) and the razor-backed musk turtle (Sternotherus carinatus). The study was conducted between 1958 and 1968 on turtles collected from Oklahoma, Arkansas, and Texas. Gonadal changes in these species have not been extensively studied, except for Risley's (1938) study of seasonal testicular changes in S. odoratus of Michigan. Tinkle (1961) found geographic variation in size, reproductive potential, and maturity of S. odoratus, but did not study seasonal gonadal changes. Detailed studies on seasonal gonadal changes have been reported for Terrapene carolina (Altland, 1951), Pseudemys scripta (Cagle, 1944, 1948), and Chrysemys picta (Gibbons, 1968). Powell (1967) described the ovarian cycle of the painted turtle, Chrysemys picta, in Nova Scotia, and Legler (1960) studied the sexual cycle of the ornate box turtle, T. ornata. More recently Ernst (1971) studied the sexual cycle and maturity of C. picta in Pennsylvania, and Moll and Legler (1971) reported on the gonadal changes of the neotropical slider turtle, Pseudemys scripta in Panama. METHODS Seasonal gonadal changes were studied in turtles autopsied within a week after capture. The gonads were examined immediately after dissection. Male turtles, sacrificed during winter months, were collected in November and kept in aquaria with water temperatures ranging between 5 and 15 C. The numbers of turtles sacrificed during each season are indicated in Figs. 1 and 2.

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