. The Biological bulletin. Biology; Zoology; Marine biology. 284 WESLEY R. COE Bay are commonly smaller than females, but found no evidence that an actual change of sexual phase might occur. It is obvious that the question can be settled only by following the growth stages during the entire life and under a variety of environ- mental conditions. Such is the object of the present investigation. In a recent publication (Coe, 1933), reporting the destruction of mooring ropes in Long Island Sound by Teredo navalis morsel (T. morsel Bartsch, 1922), mention was made of the evidence for protandry in
. The Biological bulletin. Biology; Zoology; Marine biology. 284 WESLEY R. COE Bay are commonly smaller than females, but found no evidence that an actual change of sexual phase might occur. It is obvious that the question can be settled only by following the growth stages during the entire life and under a variety of environ- mental conditions. Such is the object of the present investigation. In a recent publication (Coe, 1933), reporting the destruction of mooring ropes in Long Island Sound by Teredo navalis morsel (T. morsel Bartsch, 1922), mention was made of the evidence for protandry in that species. Rope is such an unnatural and unsuitable material for the sustenance of ship worms that normal growth is inhibited and only dwarf, or stenomorphic animals are found. Yet such individuals may reach sexual maturity and produce a relatively small number of normal. Fig. 1. Gonad of initial male phase, male type, with a few spermatozoa al- ready formed; cortical layer with only a few small differentiated ovocytes (oc) ; spg1, spg2, primary and secondary spermatogonia; spc1, spc2, primary and sec- ondary spermatocytes; spt, spermatids. gametes. All young individuals appear to pass through a functional male phase and most of them later become females. Histological study shows that the developing gonad is always more or less distinctly bisexual, each follicle consisting of an outer or cortical layer of ovocytes with a mass of spermatogenic cells filling the lumen (Figs. 1-3). Proliferation of spermatogonia proceeds rapidly and sper- matogenesis follows so quickly that the gonad may be filled with ripe spermatozoa within five to six weeks after the young animal has com- pleted metamorphosis. Before the spermatozoa have been discharged, however, the ovocytes in the cortical layer have begun the deposit of yolk in anticipation of the following female phase (Fig. 3). Entirely parallel conditions are found in T. navalis novanglice at Woods Hole (Figs. 4-6). In both these varie
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