when cut off at any other level. Schultz states that we see here an excellent example of how regeneration is influenced by natural selection, since regeneration takes place best where the leg is most often broken off. On the other hand, the author hastens to add that since regeneration also takes place when the leg is cut off at any other level, this shows that the power to regenerate is characteristic of all parts of the organism, and is not _merely_ a phenomenon of adaptation, as Weismann believes. It seems highly improbable that a spider could ever lose a leg in the middle of a segment, _i.e._ between two joints, since the segments are hard and strong and the joints much weaker; but nevertheless the leg has the power to regenerate also from the middle of the segment, if cut off in this region. The formation of the new part takes place somewhat differently, according to Schultz, when the leg is amputated between two segments than when cut off at the coxa. In the latter case, there is produced from the cut-end of the last segment a solid rod which, as it grows longer, bends on itself several times. Joints appear in the rod, beginning at the base. The leg is set free at the next moult. If the leg is cut off nearer the distal end a smaller rod is formed, that extends straight forward, or may be thrown into a series of folds. It lies, however, inside of the last segment, since the surface exposed by the cut is quickly covered over by a chitinous covering. The piece is set free at the next moult. Loeb has found that if the body of the pycnogonid, _Phoxichilidium maxillare_, is cut in two there regenerates from the posterior end of the anterior half a new body-like outgrowth.