How do urochordata differ in structure from cephalochordates?

Urochordata, or tunicates, exhibit a simple body structure characterized by a gelatinous tunic that encases their sac-like body, with adults typically displaying a sessile lifestyle. In contrast, cephalochordates, such as lancelets, have a more elongated and streamlined body plan, maintaining a notochord throughout their life. Additionally, cephalochordates possess a well-developed dorsal nerve cord and segmented muscles, while urochordates have a reduced nervous system and lack a segmented body structure in adulthood.