Which of the following animals is without a sexual medusa stage?

In which phylum are the animals characterized by cells arranged in two embryonic layers?

$A$ coral island with a central shallow lake is known as

Which of the following cells are present only in the epidermis of Hydra?
$(A)$ Interstitial cells
$(B)$ Cnidoblasts
$(C)$ Sensory cells
$(D)$ Germ cells

Metagenesis can be seen in

Jellyfish belongs to which of the following phyla?