the same gentleman to Niagara Falls and the White Mountains. The European weeds which are limited to cultivated ground, as Lychnis Githago, Centaurea cyaneus, are entirely omitted in this list, as well as plants escaped from gardens, which are found only occasionally, in an apparently wild condition, in the United States, as Abutilon Avicenna, Althea officinalis, &c.

It is still a question whether all these plants originate from Europe, as many of them occur there in the same circumstances as in this continent, under the immediate influence of agricultural improvements, and might have followed the Caucasian race of men from farther east, in his migrations over the temperate zone of Europe. Various other remarks respecting the vegetation of this continent may be found above, in the course of the Narrative, pp. 10, 13, 19, 89. Many interesting remarks upon the foreign vegetation of this continent may also be gathered in Kalm's Travels in North America. Quite a number of European insects have also been introduced into this country with those plants, among which I may mention some showy butterflies, as Vanessa atalanta, Cardui and Antiopa, which are very erroneously considered by some entomologists as native Americans.

III.

CLASSIFICATION OF ANIMALS FROM EMBRYONIC
AND PALEOZOIC DATA.

FOR several years I have been in the habit of illustrating, in my public lectures and elsewhere, principles which have not yet been introduced in our science, and to which I feel it my duty to call attention in a more formal manner on this occasion, as during our excursion we had several opportunities to discuss them at length. These remarks will form an appropriate introduction to the lists of the animals found about Lake Superior, which are given below.

The principle which has regulated our classifications for the last half century, is that which Cuvier worked out by his anatomical investigations; I mean the arrangement of the whole animal kingdom according to the natural affinities of animals as ascertained by the investigation of their internal structure. This fruitful principle, applied in various ways, has produced a series of classifications, agreeing or differing more or less in their outlines, but all resting upon the idea, that a certain amount of anatomical characters may be easily ascertained, expressing the main relations which exist naturally among animals, and affording a natural basis for classification. Structure, therefore, internal as well as external, is, according to the principles of Cuvier, the foundation of all natural classifications; and undoubtedly his researches and those of his followers have done more, in the way of improving our natural methods, than all the efforts of former naturalists put together; and this principle will doubtless regulate, in the main, our farther efforts.

Nevertheless, so much is left in this method to the arbitrary decision of the observer, that it would be in the highest degree desirable

to have some principle by which to regulate the internal details of the edifice.

We may indeed form natural divisions simply from structural evidence, bring together all fishes as they agree in the most important details of their structure, and combine all reptiles into one class, notwithstanding the extreme differences in their external form. We may also recognize the true affinity of whales, and bring them together with other Mammalia, notwithstanding their aquatic habits and their fish-like form; we may even subdivide those classes into inferior groups upon structural evidence, and thus introduce orders, like the Quadrumana, Carnivora, Rodentia, Ruminantia, &c., &c., among Mammalia. But we are at once at a loss how to determine the relative value of those groups, and to find a scale for the natural arrangement of further subdivisions. After having, for example, circumscribed the Carnivorous Mammalia into one natural family, how are we to group the minor divisions like that of the swimming Carnivora, the Plantigrada and the Digitigrada; or, after circumscribing the reptiles into natural groups like those of Chelonians, Saurians, Ophidians and Batrachians, how shall we, for instance, arrange the various types of Batrachians? To those who have been familiar with our proceedings in all these attempts, it must be evident that the grouping of our subdivisions has been almost arbitrary and entirely left to our decision without a regular guide. We have, it is true, subdivided the Batrachians into the more fish-like forms which preserve their gills and tails, or at least their tails; and into another group, containing those which undergo a complete metamorphosis; but it has not yet occurred to naturalists to take this metamorphosis as the regulating principle of classification, to arrange genera according to their agreement with certain degrees of development, in the natural order of changes which the higher of these animals undergo. Now it is my firm belief, that such a new principle can be introduced into our science; that methodical arrangement may be carried into the most minute details, without leaving any room for arbitrary decision. Proteus, Menobranchus, Amphiuma, Triton, Salamandra will hereafter have a natural place in our classification, which will be commanded by embryology, and no longer be left to a vague feeling that aquatic animals are lower than amphibious and terrestrial ones, and that the