The early development of Cavia: Note on associated remains of previous placentation

While investigating the early development of Cavia, some phenomena were observed which, when considered with reference to the implantation of the ovum, seem to be of very considerable significance. It is not proposed in this preliminary note to deal with the actual implantation process in Cavia, but simply to describe and illustrate these remarkable appearances and briefly to explain their origin. Fig. 1 (Plate 2) is a young blastocyst with the zona intact, lying, as free blastocysts usually do, in a slight and partial pouch of the ante-mesometric wall of the uterine cavity. It is noticeable that there is no reaction in the maternal tissues. Fig. 2 is a slightly older blastocyst with the zona now gone, and the central mass differentiated from the trophoblastic mass orträger . Here, also, there is no reaction in the maternal tissue. These two embryos may be regarded as normal, and are two out of a considerable series in my possession. They definitely demonstrate the fact that implantation does not occur at a stage that is any younger than that represented by the elder of these two.