two layers but so have three
Hydra was a many headed serpent in Greek mythology
The Hydra?? I think you may be referring to the Lernaean Hydra, which by varying accounts has as few as 5 and as many as 100 heads. 9, however, is the accepted standard.
two
how many tissue layers do the phylum arthropoda have
There are three layers of embryonic tissue present in the pig. These layers are called the ectoderm, mesoderm and the endoderm.
Three
There are three layers: ectoderm, mesoderm, and endoderm.
Phylum Platyhelminthes have three tissue layers: ectoderm, mesoderm, and endoderm.
It contains four layers
three
Adult amphibians have three tissue layers: the ectoderm, mesoderm, and endoderm. These layers give rise to different organs and tissues during development.
3