Complex sentence: This bend becomes dilated into a pouch, which constitutes the entodermal cloaca; into its dorsal part the hind-gut opens, and from its ventral part the allantois passes forward.
Split into simpler sentences: This bend becomes dilated into a pouch, which constitutes the entodermal cloaca. The hind-gut opens into its dorsal part, and from its ventral part the allantois passes forward.