Figure 1.

Portrait of T. H. Huxley and representative drawings of a zooid of Pyrosoma (a), a blastozooid of Doliolum denticulatum (b) and an oozooid of Thalia democratica (c). Note that, as Huxley was not aware of the close relationship between tunicates and vertebrates, the embryos are shown in reverse dorsoventral orientation with the endostyle upwards and the brain downwards. (a,c) Adapted from [2] and (b) from [1].