Many lower annelids (sagitta, phoronis, many nematoda, etc., terebratula, argiope, pisidium).

Nematoda The picture shows a hatching dog roundworm, a nematode found in dog faeces.

We find the vascular system in this very simple form to-day in the Bryozoa, Rotatoria, Nematoda, and other lower Vermalia.