Fig. 4

Variation in cnidosac entrance and exit morphology: a) longitudinal section showing a ciliated channel in Pteraeolidia ianthina (scale bar = 50 μm); b) longitudinal section showing a simple entrance from Dondice occidentalis (USNM1276036; scale bar = 50 μm); c) longitudinal section showing a discrete cnidopore in Cerberilla amboinensis (scale bar = 100 μm); and d) longitudinal section showing a simple exit in Cratena peregrina (scale bar = 50 μm). Abbreviations: cc, ciliated channel; cp, cnidophage; en, entrance; ex, exit; ffk, free-floating kleptocnide; p, cnidopore; pz, proliferation zone