Fig. 5

The external muscle lining of the testis in Quatuoralisia malakhovi. a The whole testis covered by muscle cells (mc); the frame indicates the area enlarged in figure c. b Gonad pore (gnp) surrounded by radial muscle cells. c Muscle cells (mc) of the external lining of the testis. d Contracted muscle cells at the bases of the testis lobes; frames indicate the areas enlarged in figures f–h. e Reconstruction of the lobed immature testis (blue) with the areas of contracted muscle cells (brown) at the bases of the lobes. (f–h) Contracted muscle cells (mc) at the bases of the testis lobes. ep, ectodermal epithelium; gnp, gonad pore; hs, haemal sinus; lum, lumen of the testis; mc, muscle cells; pbc, peribranchial cavity; tc, trunk coelom