-The hydra is a diploblastic unicellular organism with simple structure
-The germ/body layer comprise of the ectoderm and endoderm
-In between this germ layer is an acellular structure called mesoglea
-There is no known function of the mesoglea
-The ectoderm covers the entire body surface, found at the exterior
-While the endoderm is found in the innermost part of the body, lining the gut

Read: LOOPING in coelenterates: explanation to looping in hydra