The Woods Holl Laboratory has a right to claim a large share in the credit for three of the most important developments in biology in the last decade--the study of ‘cell lineage,’ of regeneration of organs and of the influence of abnormal conditions on the development of embryos. Workers there have traced the development of the different cells into which the egg-cell divides and have discovered just what parts of the body arise from each group of cells. They have shown that the way in which the egg divides and redivides is as constant, is as much a part of the nature of the animal, as its adult form and structure are. They have replaced previous vague notions of the development of animals by exact accounts of the cell-origin of different organs of the body. Others have studied the abilities of mutilated animals to reproduce the parts lost and the conditions and limitations of such regeneration. Such studies have greatly broadened our views of the nature of animal tissues. Others have investigated the results of artificial conditions on the development of animals, especially in the earliest stages. For instance, from eggs broken into pieces there have been developed twins, triplets and monsters of various sorts. Such experiments as these are producing data concerning the very fundaments of living matter and are leading biology beyond the mere description of animal structures and functions towards an insight into the elementary principles of development. Among the numerous researches, some seventy in all, which are being carried on at Woods Holl this summer, those of the most general interest are Prof. C. O. Whitman’s study of hybrids and Prof. Jacques Loeb’s study of artificial fertilization. Prof. Whitman has been breeding pigeons of a large number of species for several years, as a means of studying the phenomena of heredity shown in hybrid forms. More or less incidentally, he has discovered many notable facts about the instincts and habits of the birds and about various physiological functions connected with reproduction. Biologists everywhere are coming to realize the necessity of systematic and continuous study of families of animals through a number of generations. Prof. Whitman’s is the most extensive of such studies in this country. The detailed results of Prof. Loeb’s continuation of his experiments on the action of various salts on unfertilized eggs will naturally be awaited with great interest. We have already noticed his success in causing unfertilized eggs of the sea-urchin to develop into normal individuals as far as the pluteus stage. He has this year succeeded in producing artificial parthenogenesis not only in starfish (_Asterias_), but also in worms (_Chaetopterus_). Through a slight increase in the amount of K-ions in the sea-water, the eggs of the latter can be caused not only to throw out the polar bodies as Mead had already observed, but also to reach the _Trochophore_ stage and swim about as actively as the larvæ