. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 23G Mr. C. P. on the FholadUx. rapidly to great size, and is very destructive. The sexes are separate and of about equal proportions. I found specimens sexually mature during the spring and until the middle of July. The breeding-season probably lasts all summer. The eggs are cast into the water, and, if the sexual products are mature, they are extruded through tlie siphons when the animals are taken from their tubes. The eggs are of about the same size as those of P
. The Annals and magazine of natural history; zoology, botany, and geology. Natural history; Zoology; Botany; Geology. 23G Mr. C. P. on the FholadUx. rapidly to great size, and is very destructive. The sexes are separate and of about equal proportions. I found specimens sexually mature during the spring and until the middle of July. The breeding-season probably lasts all summer. The eggs are cast into the water, and, if the sexual products are mature, they are extruded through tlie siphons when the animals are taken from their tubes. The eggs are of about the same size as those of Pholas, but more opaque and of somewhat slower cleavage. The segmentation of tlie egg and the derivation of the germ-layers are step by step as in Pholas, so that to describe them would be but a repetition of every detail—planesof cleavage, establishment of bilateral symmetry, gastrulation and division of the entoblast-cells, double origin of the mesoblast, ciliation and rotation of the embryo, per- sistence of the crescent-shaped blastopore as the mouth. The accompanying figure represents a longitudinal section. of an embryo of T. norvegica with eight entoblast-cells. The apical end is to the riglit. The posterior mesoblast, /)/n, lies in the cleavage cavity, as does also the smaller anterior meso- blast, am, upon the entoblast-cells. The four entoblast-cells shown are of subequal size. The shell-gland is just beginning to form. Teredo {Xylotrya) fimhriata. This species is equally as abundant at Beaufort as the preceding, but of smaller size. The sexes are separate and of about equal {proportions. The eggs develop in the water, but are not extruded as are those of T. norvegica. They are easily fertilized artificially and develop rapidly. The embryos are hardy in aquaria. Except for tlie greater opacity of the egg, I think it impossible to distinguish the segmenting Qg^ and embryo from those of Pholas. All of the features sum- marized for Pholas are true for this species. Tere
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