Fish 164 General conclusions 172 Bibliography 176 BULLETIN OF THE BUREAU OF PISHEKIES carried on by Dr. H. B. Bigelow, are published in a series of bulletins from the Museum of Comparative Zoology at Cambridge, Mass., and a more complete account of these investigations and explorations is now in process of publication. It has long been known that Woods Hole occupies a unique position on the Atlantic coast. It is the northern limit of many southern forms and the southern limit of many northern forms. Oceanic animals, also, are often carried into this pocket on the coast by the southerly winds and strong tides that prevail in the summer months. For that reason Woods Hole was selected as an ideal location for the study of plankton and the interrelationships of the various pelagic faunas. Under "plankton" I have included all animals occurring in surface collections, whether free-swimming or carried by currents. Such a broad definition includes a great many benthonic forms carried from their natural habitat by storms or high winds, but in a littoral region one can not always decide accurately which species have been accidentally carried to the surface and which are free-swimming. The present paper is the result of a continuous investigation of the plankton in Great Harbor, Woods Hole, Mass., covering a period of two years. The pin-pose was to make an exhaustive qualitative study of the plankton of this region, the seasonal distribution of the various species, their interrelationships, and the general factors governing their distribution. The investigation consisted of three parts: (1) An examination of plankton samples taken daily during the years 1899 and 1900 in Great Harbor by the late Vinal N. Edwards, collector for the United States Fish Commission; (2) a survey of aU records of surface collections of previous years; and (3) examination of hving material taken daily in surface collections in Great Harbor, observations on temperature, salinity, and other factors governing the seasonal distribution of the plankton, and a survey of the general geography of the region as a factor affecting plankton distribution. The first part of the investigation occupied the entire time of the author during the year 1921-22 and was carried on in the biological laboratory at Brown University. Many of the fragile animals had become disintegrated during the 22 years in which the material had remained untouched, and the preservatives in some of the samples had evaporated. Over 200 vials remained intact, however, and offered ample material for study. The second part of the work involved much time and proved to be a very tedious task. The results, however, were very important, as they covered the daily records of surface collections extending over a period of 15 years-1893 to 1907, inclusive. The larval fish and coelenterates taken during this time had been carefully identified by Vinal N. Edwards. Diatoms, copepods, amphipods, annelids, and other planktonic forms were recorded as groups, the relative abundance for each day bemg carefull...