Question

flatworms are devoid of​

Answer 1

Explanation:

Flatworms are unsegmented, bilaterally symmetrical worms that lack a coelom (acoelomate) but that do have three germ layers. Some forms are free living but many are parasitic.

Answer 2

Flat­worms are un­seg­mented, bi­lat­er­ally sym­met­ri­cal worms that lack a coelom (acoelo­mate) but that do have three germ lay­ers. Some forms are free liv­ing but many are par­a­sitic. Flat­worms have a cephal­ized ner­vous sys­tem that con­sists of head gan­glion, usu­ally at­tached to lon­gi­tu­di­nal nerve cords that are in­ter­con­nected across the body by trans­verse branches. Ex­cre­tion and os­moreg­u­la­tion by flat­worms is con­trolled by "flame cells" lo­cated in pro­tonephridia (these are ab­sent in some forms). Flat­worms lack a res­pi­ra­tory or cir­cu­la­tory sys­tem; these func­tions take place by ab­sorp­tion through the body wall. Non­par­a­sitic forms have a sim­ple, in­com­plete gut; even this is lack­ing in many par­a­sitic species.

Move­ment in some flat­worms is con­trolled by lon­gi­tu­di­nal, cir­cu­lar, and oblique lay­ers of mus­cle. Oth­ers move along slime trails by the beat­ing of epi­der­mal cilia. The de­vel­op­ment of di­rec­tional move­ment is cor­re­lated with cephal­iza­tion. In some flat­worms, the process of cephal­iza­tion has in­cluded the de­vel­op­ment in the head re­gion of light-sen­si­tive or­gans called ocelli. Other sense or­gans found in at least some mem­bers of this group (not nec­es­sar­ily on the head) in­clude chemore­cep­tors, bal­ance re­cep­tors (sta­to­cysts), and re­cep­tors that sense water move­ment (rhe­o­re­cep­tors).

Explanation:

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