In the male, cells of the posterior lateral seam generate the sensory rays, instead of alae. hyp cells of the tail tip reorganize to form a blunt tail morphology. The hypodermis (or lateral seam) secretes the cuticular fan in which the sensory rays are embedded. Internally, rectal epithelial cells (B, F, and U) divide to produce the proctodeal and cloacal lining of the reproductive tract, replacing the rectum. The B lineage also generates the support cells (and neurons) of the spicules. Ventrally, hypodermal P cells in the posterior generate the hook. The rectal epithelial cell Y produces the support cells (and neurons) of the PCS, which lies posterior to the hook. In hermaphrodites, P cells in the mid-body make the vulval epithelium. Reprinted with permission from Wormatlas (http://www.wormatlas.org).