HUBRECHT. PG Tt 
AY 50 
Fig. 49. Longitudinal section of another Tarsius blastocyst in which the 
protochordal plate f has become fairly established and the protochordal wedge 
is just in its very earliest phase, more so than in Fig. 48. The ventral meso- 
blast vw arises from the ectoderm, close behind fw: the trophoblast ¢, is inde- 
pendent of both. — Fig. 50. Longitudinal section in about the same stage: 
the attachment of the blastocyst to the uterine wall commences about at the 
spot marked ¢r: the corresponding proliferation of trophoblast (¢) is not in- 
dicated in this figure (cf. Fig. 62); the ventral mesoblast 7 springing from the 
ectoderm shows the extraembryonic coelom the wall of which is partly splanchnic 
(spm), partly somatic mesoblast (som); pp protochordal plate. -—— Fig. 51. Trans- 
verse section of an early blastocyst of about the stage of fig. 46 showing the 
proliferating protochordal plate. 
