Although we are writing a preface to our first series already closed, we may, without impropriety, say something of the Second Series now in successful progress. It began on the first of January, 1846; instead of being quarterly like the First Series, it appears once in two months--six times in a year, giving two volumes of 450 pages each. In this Series, the name of a third editor appears upon the title page, and the remarks which have been already made are, in their spirit and almost in the letter, applicable in the present instance. The _unity_ is still preserved, and both counsel and action--favored by juxta-position and constant intercourse--are almost as if one individual presided alone. It will be perceived, therefore, that we have not departed from the principle which has governed us from the beginning, and when our mantle shall fall, there are those at hand who may, if it be worth the effort, arrest it in its descent and wear it more worthily than we have done. * * * * * The portrait prefixed to this volume was engraved for a very different purpose and for others than the patrons of this Journal. It has been suggested by friends, whose judgment we are accustomed to respect, that it ought to find a place here, since it is regarded as an authentic, although, perhaps, a rather austere resemblance. In yielding to this suggestion, it may be sufficient to quote the sentiment of Cowper on a similar occasion, who remarked--"that after a man has, for many years, turned his mind _inside out_ before the world, it is only affectation to attempt to hide his face." * * * * * In tracing back the associations of many gone-by years, a host of thoughts rush in, and pensive remembrance of the dead who have labored with us casts deep shadows into the vista through which we view the past. Anticipation of the hour of discharge, when our summons shall arrive, gives sobriety to thought and checks the confidence which health and continued power to act might naturally inspire, were we not reproved, almost every day, by the death of some coeval, co-worker, companion, friend or patron. This very hour is saddened by such an event,--but we will continue to labor on, and strive to be found at our post of duty, until there is nothing more for us to do; trusting our hopes for a future life in the hands of him who placed us in the midst of the splendid garniture of this lower world, and who has made not less ample provision for another and a better. Yale College, April 19, 1847. EXPLANATIONS. Names of authors and subjects are arranged together alphabetically. References to species of animals described or noticed in the Journal, though to some extent distributed through the Index, are systematically catalogued under the word _Zoology_. The same plan is followed with _Botany_. Obituary notices are collected together under _Obituary_.