Figure 1.

Post-implantation development of AND, PAR and CTR sheep conceptuses. (a) Similar size and gross morphology of AND, PAR and CTR conceptuses at day 20 of development: all had optical vesicles, two to three pharyngeal bars and closed anterior neurophores. Living (with beating heart) AND conceptuses were collected exclusively at day 20, and living, though growth-retarded, PAR conceptuses at days 22 and 24. PAR conceptuses lacked posterior limb buds and optical lens pigmentation and had reduced head size. (b) Most day 20 conceptuses developed to the 20 somite stage, independently of the group to which they belonged.