The golden hamster (Cricetus auratus), first described by Waterhouse (1839)' has been widely adopted as a laboratory animal since its introduction into England in 1931.
The breeding and growth of the hamster have been described by Bruce and Hiiidle ( '34) and by Sheehan and Bruner ( '45). Laidlaw ( '39) discussed the problems associated with the maintenance of a colony and Cooperman, Waisman and Elvehjem ( '43) described the nutritional requirements of the hamster .
The only developmental studies available are the note of Ochs ( '08) and the unpublished thesis of Graves ( '43). Kent and Smith ('45) gave a detailed discussion of the estrous cycle and Sheehan and Brunner ( '45) also mentioned the cycle. Deanesly ('35) presented data on the reproductive cycle with emphasis on the histology of the genital tract in the various stages. The ovary was described but there was little inforniation on the ova themselves.
Hamilton ('42) and Samuel ('44) both illustrate early hamster ova but do not give the exact age of these specimens.
Samuel and Hamilton ('42) report several living hamster eggs at each of the following stages of development : unsegmented unfertilized, unsegmented fertilized, 2-cell stage, 4-cell stage, and 8-cell stage. Gravcs reports 110 pre-implantation ova which he states were dated from observed copulation. This report adds 74 pre-implantation stages.