Scheme of the surgical ablation of sexual worms. By surgical ablation, 3 different fragments were obtained with respect to the topological position of the sexual organs: the head (H) fragment had no sexual organs; the middle (M) fragment had a pair of ovaries, testes, and yolk glands; the tail (T) fragment had testes, yolk glands, and a copulatory apparatus. Coloured regions correspond with the sexual organs: red, ovary; blue, testis; yellow, yolk gland; green, a copulatory apparatus with a genital pore. The white region in the body is the pharynx. Figure 2 in Kobayashi et al  was modified.