Noun
The pore or opening leading into the cavity of invagination, or archenteron.
Source: Webster's dictionaryDuring the early development of the embryo, in deuterostomes, the blastopore (the first opening to form) becomes the anus whereas in the protostomes, it becomes the mouth. Source: Internet
In most bilaterian embryos the blastopore, a dent in the outer wall, deepens to become the larva's gut, but in ectoprocts the blastopore disappears and a new dent becomes the point from which the gut grows. Source: Internet