Biology 11th Edition by Gerald Audesirk,Teresa Audesirk,Bruce Byers

تمرين 18

In chordates, the nerve cord is ______________ and runs along the ______________ side of the body. During at least one stage of a chordate's life, it has a tail that extends past its ______________ and its body is stiffened by a(n) ______________ that runs along its length.