Blastopore develops into mouth in

Blastopore is the external opening of the primitive gut (archenteron) in the gastrula. 

In protostomes (Gr. protos = first; stoma = mouth) mouth develops from the blastopore. A second opening of archenteron formed later at the opposite end becomes the anus. 

In deuterostomes (Gr. deuteros = second; stoma = mouth) blastopore forms the anus. Mouth is derived from the secondary opening of the archenteron.