Ans. When the evolutionary dynamics of invertebrates are considered, trochophore larva attracts special attention as it shows prominent similarities with some other groups of invertebrates. The affinities with other groups suggest to conclude that the animals having bilateral symmetry emerge from those of having radial symmetry. It is assumed that the trochophore represents a transitional stage in the line of emergence of the bilateral groups (Ctenophores). Similarities between the trochophore and the echinoderm larva (Bipinaria and Pluteus) and Tornaria larva of Balanoglossus added more weight to this idea.