HUBRECHT. Pl. FE. 
Fig. 28. Section through an early blastocyst 
of the mouse (after Selenka, “S3).. @ amnion, on 
the point of being constricted off. 2 Ectodermal 
shield. mes mesoblast. ex entoderm. /¢r tropho- 
blastic rudiment of placenta. — Fig. 29 to 32. Four 
successive stages in the early development of Tu- 
paja javanica. In Fig. 29 the trophoblast ¢- yet forms a solid closed sac round 
embryonic knob and entoderm, the latter only just beginning to split off from 
the embryonic knob as far as its embryonic portion is concerned. In Fig. 30 
and 31 the bent embryonic ectoderm cc commences to free itself from its tro- 
phoblastic covering; in Fig. 32 it has quite flattened out, forming the embryonic 
shield on the top of the spherical blastocyst. 
