Fig. 4

Growth via cellular proliferation in. P. lividus. a–h’ Proliferation on aboral (a, c) and oral (b, d, e, f, g–h’) surfaces in J2 animals. e, f Close-ups of proliferating cell doublets in 24-h post-chase animal (e) and quadruplets in 48 h post-chase animal (f). g–h’ Zoom showing proliferative zone associated with plate addition. i–j Cell proliferation associated with the addition of new ambulacral spines and secondary podia in J5 animal. k Graph showing differential cell proliferation on oral and aboral surfaces. Abbreviations as in Fig. 2. Scale bars in a–d 200 μm, e–f 10 μm, i–j 100 μm, and g–h 50 μm