FIG. 12. Undischarged p-mastigophores B2a of acontia in different species and various degrees of development. Sagartiidae sp.: A, immature nematocyst with broad capsule and looped proximal and main shaπ; B, immature nematocyst with broad capsule and undulating proximal and main shaπs; C, immature nematocyst with looped proximal shaπ; D, immature nematocyst with undulating proximal shaπ and distinct limit between proximal and main shaπ; E, nematocyst late in development showing shorter, straighter proximal and main shaπ with visible central rod-shaped rod on proximal shaπ; F, mature nematocyst with slender capsule and internal capsular matrix visible, straight shaπ with indistinct central rod-shaped structure on proximal shaπ and indistinct limit between proximal and main shaπ. Scale bars: A–F, 10 µm.