ABSTRACT
Hind guts of -day mouse embryos were transplanted into the posterior part of the coelomic cavity of
-day chick embryos. The hosts were sacrificed after 1–7 days and the mouse primordial germ cells (PGCs) in the graft and in the surrounding host tissues were searched for by means of the histochemical technique for alkaline phosphatase. Altogether 94 grafts were examined.
During the first 3 days of intracoelomic development of the graft accumulations of mouse PGCs close to the mesonephros, the mesentery or the gonad of a chick embryo were observed in 26 out of 51 cases. In 12 grafts single PGCs crossed the boundary between the host and the graft and settled in host tissues such as the mesonephros, the mesentery or the gonad.
After 3 days mouse PGCs are no longer visible in the chick tissues. However, the number of PGCs in the grafts also gradually decreases and from the 4th day onwards many of the grafts contain no PGCs. The ability of mouse PGCs to survive extragonadally, even in the embryonic hind gut, is thus limited.
In some of the 4-to 7-day-old grafts PGCs occur on the periphery of the graft in the form of single aggregations. From the 6th day the only PGCs which survive are those in aggregations.
The experiments indicate that the gonads, together with adjacent tissues (mesonephros, mesentery) of a chick embryo are attractive to mouse primordial germ cells and that the hypothetical attractive substance is not species specific.