Question: During coelom development in protostomes. Need Assignment Help? Multiple Choice the mesoderm forms a pair of pouches that eventually fuse together. These pouches go on to enlarge and form the coelom. the endoderm forms a pair of pouches that eventually fuse together. These pouches go on to enlarge and form the coelom. the endoderm is formed from cells located near the blastopore. The endoderm then splits to form the coelom. the mesoderm is formed from cells located near the blastopore. The mesoderm then splits to form the coelom.