Neurons are amitotic, which means that after a certain stage, they do not divide further. most tumor cells are

neuroglial cells;  since neuroglial cells are capable of mitosis

Complete question: “Neurons are amitotic,  which means that, after a certain stage, they do not divide further.  Most tumor cells are characterized by a rapid rate of mitosis. Based on this, of which cell types brain tumors be composed (neurons or neuroglia)? Why”

Brain tumors are composed of neuroglia, the non-neuronal cells in the central nervous system that maintains homeostasis, form myelin,  provide support and protection for neurons and capable of mitosis.

Tumor cells multiply relentlessly in the absence of growth-promoting factors for proliferation of normal cells and resistant to signals that program apoptosis. Cancer cells continue to produce copies when there is no need. The copies continuously divide serving no purpose. It can also spread to nearby and distant tissues.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.