had only to speak, and such a currency of _plastrons_ and _carapaces_ was set in circulation, that the contemplative stranger who saw the mighty coinage of Chelonia flowing in upon Cambridge might well have thought that the national idea was not the Almighty Dollar, but the Almighty Turtle. Mr. Agassiz places a high estimate on the intelligence as well as the kind spirit of his adopted countrymen. "There is not a class of learned men here," he says, "distinct from the other cultivated members of the community. On the contrary, so general is the desire for knowledge, that I expect to see my book read by operatives, by fishermen, by farmers, quite as extensively as by the students of our colleges, or by the learned professions; and it is but proper that I should endeavor to make myself understood by all." The deficiencies of our scientific libraries, and the want of a class of elementary works upon Natural History, such as are widely circulated in Europe, are adverted to and alleged as a reason for entering into details which the professional naturalist might think misplaced. We quote one paragraph entire from the Preface, as not susceptible of being abridged, and as briefly stating those general facts with regard to the work which all our readers must desire to know. "I have a few words more to say respecting the two first volumes, now ready for publication. Considering the uncertainty of human life, I have wished to bring out at once a work that would exemplify the nature of the investigations I have been tracing during the last ten years, and show what is likely to be the character of the whole series. I have aimed, therefore, in preparing these two volumes, to combine them in such a manner as that they should form a whole. The First Part contains an exposition of the general views I have arrived at thus far, in my studies of Natural History. The Second Part shows how I have attempted to apply these results to the special study of Zoology, taking the order of Testudinata as an example. I believe, that, in America, where turtles are everywhere common, and greatly diversified, a student could not make a better beginning than by a careful perusal of this part, specimens in hand, with constant reference to the second chapter of the First Part. The Third Part exemplifies the bearing of Embryology upon these general questions, while it contains the fullest illustration of the embryonic growth of the Testudinata." The Preface closes with honorable mention of the gentlemen who have furnished direct assistance in the preparation of the work, and especially of Mr. Clark in microscopic observation and illustration, and of Mr. Sonrel in drawing the zoological figures.