The P5.p, P6.p and P7.p VPCs divide three times to produce 22 progeny. The vulval progeny differentiate to give rise to 7 different cell types (vulA to vulF). The homologous cells from P5.p and P7.p lineages fuse selectively to form 7 concentric toroids that are interconnected via AJM-1-containing apical junctions. During the mid-to-late-L3 stage the AC initiates invasion into the vulval epithelium. At the early-L4 stage it can be seen establishing the lumen in vulF thereby promoting a connection between vulva and uterine lumens. By the mid-L4 stage AC has fused with π progeny to form the utse cell and its nucleus has migrated (either anteriorly or posteriorly) away from the connection between the two lumens.