The American Arbacia and other sea urchins

Abstract

The sea urchin, Arbacia punctulata, which occurs along the Eastern coast of North America, has for many years provided material for experi- mental work on cells, done mostly at the Marine Biological Laboratory at Woods Hole, Mass. The animals are readily obtained and the eggs are produced in large quantities throughout the summer. This species is the American Arbacia and is not found in Europe, where another species, Arbacia lixula occurs. The latter species and many other genera of sea urchins have been used for experimental work at Naples, on the Swedish coast, in the British Isles, France, Japan, and elsewhere. The eggs are fundamentally similar but differ in details. The Arbacia egg is an ideal cell. It iswatching its development. The granules in the egg can be moved by centrifugal force, and the egg can be broken into halves and quarters containing different kinds of materials in definite amounts. The ex- perimental work on sea urchin eggs has included every line of approach, cytology, embryology, physiology, and biochemistry, and has been concerned with the solution of many fundamental problems. The earliest experiments on Arbacia punctulata eggs were those of Jacques Loeb at Woods Hole in 1892, who wrote a paper entitled "Investigations in Physiological Morphology. III. Experiments on Cleavage", published in the Journal of Morphology. It dealt with divi- sion of the nucleus without cleavage of the cell, caused by hypertonic sea water. The next paper was that of T.H. Morgan in 1893, published in the Anatomische Anzeiger, part of which was on the same subject, taking exception to some of Loeb's results. Loeb and Morgan were succeeded by many well-known biologists. We have a fine heritage of experimental research on the Arbacia egg, and it is partly in an endeavor to gather together this work and make it more readily available to later investigators that this book has been written. The book is urchins in general—their history, which begins before Aristotle and spherical, thus rendering changes in size easy to determine. It is fairly simple in comparison with most cells. It is quite hardy and can be subjected, without damage, to moderate changes in the sea water, produced by the addition of water, or salts, or anaesthetics, or other chemicals, and to changes in temperature, pressure, light, and other physical factors. Harmful ef- fects and recovery can be readily detected by fertilizing the egg and