Cites figs. XV and XVI:

'Origin of the pigment. It is almost invariably found with a basis of proteid substance which in the living cell is irregularly spherical or readily separates out in such a form on teasing. The colouring matter appears to be in two conditions; it impregnates the basis and, possibly because then diffused, is a brighter, lighter brown, and it occurs as small dark angular or crystalline fragments adherent to the substance which the lighter colouring matter stains throughout. Sometimes specimens of Hydra are found in which the diffuse pigment is conspicuous, while others are almost entirely tinted by well-defined lumps of pale or colourless substance bearing dark, angular, perhaps crystalline particles [note: 'Cf. Howes. Atlas of Biology, Pl. XVII. figs. XV. XVI.') (fig. 9, a, b, c, Pl. VI.). The former animals are bright brown when seen macroscopically; the latter a darker greener brown.' (328)