THE single species of the sword-fish, Xiphias gladius Linnaeus, is worldwide in distribution, being found on both sides of the Atlantic and Pacific oceans, in the Indian Ocean, and in the Mediterranean Sea. Therefore, certain common breeding grounds or areas of intermingling and breeding must exist to maintain constant specific characteristics for such a widely distributed species. Such regions are not known. M. P. Fish (1926) reports that spawning sword-fish are found in the Mediterranean Sea during the late spring and early summer, and that sword-fish eggs are sometimes seen on the Sicilian coastline during this time. However, I have been unable to find any other description of the breeding habits, of the sexually ripe fish, or of schools of young sword-fish fry, in the literature on the Mediterranean swordfish. Lutken (1880) describes several young sword-fish fry captured in the middle of the Atlantic Ocean, suggesting that sword-fish might breed in the deeper waters of the Atlantic basin. There is no further evidence for this idea. Knowledge concerning the reproductive condition or breeding habits of those sword-fish occurring along the eastern American coastline is likewise scanty; for with few exceptions the several papers published on this fish as it is found in these waters are taxonomic descriptions or records of distribution. Thus the life history of the sword-fish is unknown. This lack of information leaves a wide gap in fisheries data on an economically important food fish, which would prove serious should conservation measures ever be necessary. Declining yearly catches of sword-fish along the southern New England coastline indicate that such might be the case in the future. In studying the life history of any fish, the locating of its breeding grounds is of prime importance. Once this is done, further work concerning the various phases of the problem are greatly facilitated. Such a method was used by Schmidt in his memorable work on the eel. Unfortunately, the apparent lack of spawn or numbers of sword-fish fry in the oceans prohibits the use of tow-nets in locating spawning areas. The next best approach to the problem seems an extensive study, world-wide if possible, of the reproductive glands and their state of sexual development in the adult fish, in all portions of its range. Such a study should reveal an area or areas where the swordfish are at a stage of maximal reproductive activity. Further work in such regions could be intensified until the actual breeding grounds were located. With this plan of attack, an anatomical and cytological examination of the reproductive organs of those sword-fish found off the southern New England coastline was begun in the summer of 1941. With the aid of several commercial fishing boats, gonads were obtained from 13 sword-fish during the