In the department of Mollusca, if the above principles are correct, embryology is likely to introduce modifications in our systematic methods, which will entirely overthrow the views entertained at present respecting their systematical arrangement; not that we should ever be led to consider Acephala as higher than the Gasteropoda, or these as higher than the Cephalopoda; but within these classes, taken by themselves, I look for considerable changes, which, when once introduced, might explain why there is apparently so little agreement between the geological succession of their types and their systematic arrangement, especially among Gasteropoda. Now it is precisely among these, that I anticipate the greatest changes. It is indeed a remarkable fact, that so many, if not all naked branchiferous Gasteropoda should be provided with a shell in their early age, and lose this protecting envelop as they grow older, which would lead to the conclusion, that among these animals the fact of having a shell indicates a rather lower condition. The comparison of Octopus, Loligo, Sepia and Nautilus would lead to similar conclusions. Indeed it is scarcely any longer doubted, that Nautilus has many points of resemblance in common with the Gasteropoda, and from its numerous tentacles (multiplication being always an indication of a lower degree,) must be considered the lowest type among Cephalopoda; next we should place the Dibranchiate Cephalopoda, among which the Argonauta, with its external shell, ranks the lowest; next the naked Octopodidae, while the Sepiade with their ten tentacles and internal shell or bone would be the highest in that class. Now if this arrangement be the real order of succession of the Cephalopoda accord skin of the caterpillar, (in which state the caterpillar is so seldom examined, from fear of disturbing it in its transformation) that under this last skin of the caterpillar, I say, the young butterfly assumes the characters of a Coleopteron. It has then an upper pair of wings, having the character of elytra, and a lower pair of membranous wings. At that time its jaws have not yet assumed the form of a sucker, and are still free, as are also the legs. But these parts, which are easily observed in caterpillars immersed in diluted alcohol at the very moment when they are casting their last skin, are soon soldered together to form the hard coating of the pupa, and are cast off before the perfect butterfly comes out. It is, therefore, correct to say, that the structural condition of Coleoptera, in their perfect state, answers to that stage of moulting of Lepidoptera which precedes their perfect development. Coleoptera are, therefore, one stage behind Lepidoptera; they rank below them; they are an inferior degree of development of the type of insects. ing to their structure and development, is it not remarkable, does it not indicate the maintenance of the same plan throughout the creation, when we find chambered shells, so abundant throughout the ancient geological formations, and belemnites, the analogues of the cuttle-fish, beginning late in the secondary epoch in the lias; whilst fossil argonauts do not occur before the tertiary times? So that we might almost conclude, that in this class the order of succession of their fossil types is a safer guide for our classification, than anatomical investigation. In the class of Acephala the low position of brachiopods in the order of appearance in time, as well as in our estimation of their structural standing, is another striking instance of the correspondence between the order of geological succession and the gradation in structure. I may add as a link for farther inference, that I have seen embryonic cyclas attached by a byssus to the gills of the mother. There is perhaps no department in which we may expect more important results for methodical arrangement from embryological researches than that of the Radiata. Let us only consider the metamorphosis of the Medusa, their first polyp-like condition, their division and the final transformation of their stem into several distinct individuals, exemplifying in a higher sphere the growth of compound Polypi, where the successive buds remain united upon a common stock. Let us remember the free Comatula growing from the egg upon a Crinoid-like stem; let us then remember, that there are animals of that class, which preserve throughout life this articulated support, and remind us of corals even in the highest class of Radiata; let us farther know, that even the arrangement of plates in those Crinoids agree in some respects with the first formed calcareous granules in free moving starfishes; let us finally and above all here remember, that those Crinoids with stems are only Echinoderms of earlier ages, which die out gradually, to be replaced by new and free forms, and there will not be the slightest doubt left in our minds, that besides the structure, there is no safer guide to the understanding of the plan of the creation of the animal kingdom, as it has been in former ages and as it is in our days, than embryological and palæontological researches. The internal arrangement of these classes as I now conceive it, would require that we introduce Bryozoa among Acephala and place them lowest in that class, next the compound and simple Ascidia, and then the Brachiopoda and true Acephala. Among Gasteropoda I would introduce Foraminifera as their lowest type, exemplifying, in a permanent condition, the embryonic division of their germ, next the Pteropoda would follow, also as an embryonic form of Gasteropoda, in which the lateral fin-like appendages and the symmetrical shell remind us of the deciduous shell of naked Gasteropoda with their vibrating wheels, and next the Heterobranchia, the common branchiferous Gasteropoda, and uppermost the Pulmonata, in some of which the embryo is not even aquatic, nor provided with fringed appendages. As for the Cephalopoda, I have recently had sufficient evidence from embryonic investigations that the Octocera stand below Decacera. IV. GENERAL REMARKS UPON THE COLEOPTERA OF LAKE SUPERIOR. BY JOHN L. LECONTE, M. D. THE materials which form the basis of the present catalogue, were not altogether derived from explorations made during the expedition which produced this volume. They embrace the results of my collections during three journeys made to Lake Superior, and were procured at various points around the entire circumference of that sheet of water, and during various months from June to October. The distribution of species does not appear to differ materially on the two sides of the lake; nevertheless many species occurred on the north shore, which were not found on Point Kewenaw, while many water beetles were taken at the last mentioned place, which were not seen during the present voyage. Still in each case the delay at particular localities was so short, that necessarily many even of the most common species would be overlooked. We may therefore conclude, that although the evidence is not yet sufficient to enable us precisely to distinguish between the products of the different portions of the Lake Superior region, we still have abundant material to give a tolerably complete conspectus of the character of the entire coleopterous fauna. The whole country being still almost in a primitive condition, the specimens are equally distributed throughout a large space: the woods will not therefore be found very productive to the collector. In fact nearly all the species were found adjacent to small streams; or else they were driven on shore, particularly on sand beaches, by the winds and waves after being drowned in the lake. So productive was the last method of collecting, that on one occasion more than three hundred specimens of Coleoptera, and many insects of other orders were procured in less than one hour. There are, however, a few points to which the attention of the future explorer may be directed, as being most likely to reward him for his arduous journey; these are Eagle Harbor on Point Kewenaw, the Hon. Hudson Bay Co.'s fort at the mouth of Pic River, and the islands adjacent to the mouth of Black Bay. For the sake of making the catalogue as concise as possible, I have used such abbreviations as will render necessary a list of the works cited. Where no authority is appended to a name, it is to be understood that the name is used for the first time in this book. Rarely two references are placed after a name; in this case the latter citation is the more recent, and will be found to give all necessary information respecting synonyms, which are accordingly omitted here. BOOKS CITED IN THE CATALOGUE. Am. 1r. Transactions of the American Philosophical Society. New Series. B. J. Boston Journal of Natural History. Beauv. Palisot de Beauvois. Insects d'Afrique, et d'Amerique. Dej. Spécies Général des Coléoptères de la Collection de M. le Comte Dejean. Dej. Cat. Catalogue des Coléoptères de sa Collection. Er. Erichson, Monographia Staphylinorum. Er. Col. March. Erichson, Die Käfer der Mark Brandenburg. Enc. Encyclopédie Méthodique. Fabr. El. vel F. El. Fabricius Systema Eleutheratorum. Grav. Micr. Gravenhorst, Coleoptera Microptera. Germ. Ins. Nov. Germar, Insectorum species novæ aut minus cognitæ. Gyll. Fn. Suec. Gyllenhal, Fauna Suecica. Hbst. Col. Herbst, Natursystem aller bekannten Insecten: Käfer. J. Ac. Journal of the Academy of Natural Sciences of Philadelphia. J. Ac. N. S. Ejusd. op. series nova, 1848. Kb. N. Z. Kirby in Fauna Boreali-Americana. Vol. 4. |