| The terms ectoderm and entoderm were introduced by Allman in 1853 for the two cell-layers in the Hydrozoa. |
| They are developed from the entoderm of the third and fourth branchial grooves. |
| This double disposition of the cloaca is accomplished by gradual changes in the entoderm and mesoderm. |
| Also almost any part of the animal containing both ectoderm and entoderm can be cut off and will develop into a new animal. |
| The body consists of two layers of cells, the ectoderm on the outside and the entoderm lining the digestive cavity. |
| The two layers of the gastrula may now be spoken of as ectoderm and entoderm. |
