[9]. It proved in the sequel unnecessary to seek the glacial phenomena of tropical South America in its highest mountains. In Brazil the moraines are as distinct and as well preserved in some of the coast ranges on the Atlantic side, not more than twelve or fifteen hundred feet high, as in any glaciated localities known to geologists in more northern parts of the world. The snow line, even in those latitudes, then descended so low that masses of ice formed above its level actually forced their way down to the sea-coast.—L. A.
[10]. In copying the journal from which these notes are taken, I have hesitated to burden the narrative with anatomical details. But for those who take an interest in such investigations it may be well to add here that the frog, when first hatched, is simply an oblong body, without any appendages, and tapering slightly towards its posterior end. In that condition it resembles the Cecilia. In its next stage, that of the tadpole, when the extremity has elongated into a tail, the gills are fairly developed, and it has one pair of imperfect legs, it resembles the Siren, with its rudimentary limbs. In its succeeding stages, when the same animal has two pairs of legs and a fin around the tail, it recalls the Proteus and Menobranchus. Finally the gills are suppressed, the animal breathes through lungs, but the tail still remains; it then recalls Menopoma and the Salamanders. At last the tail shrinks and disappears, and the frog is complete. This gives us a standard by which the relative position of the leading groups of the class may safely be determined.—L. A.
[11]. On account of the many exploring expeditions for which the Bay of Rio de Janeiro has been a favorite port, it has acquired a special interest for the naturalist. It may seem at first sight as if the fact that French, English, German, Russian, and American expeditions have followed each other in this locality, during the last century, each bringing away its rich harvest of specimens, by diminishing its novelty would rather lessen than increase its interest as a collecting ground. On the contrary, for the very reason that the specimens from which the greater part of the descriptions and figures contained in the published accounts of these voyages were obtained from Rio de Janeiro and its neighborhood, it becomes indispensable that every zoölogical museum aiming at scientific accuracy and completeness should have original specimens from that very locality for the identification of species already described. Otherwise doubts respecting the strict identity or specific difference of specimens obtained on other parts of the Atlantic shore, not only in South America but in Central and North America, may at any time invalidate important generalizations concerning the distribution of animals in these seas. From this point of view, the Bay of Rio de Janeiro forms a most important centre of comparison, and it was for this reason that we made so prolonged a stay there. Although the prospect of discovering any novelties was diminished by the extensive investigations of our predecessors, I well knew that whatever we collected there would greatly increase the value of our collections elsewhere. One of my special aims was to ascertain how far the marine animals inhabiting the coast of Brazil to the south of Cape Frio differed from those to the north of it, and furthermore, how the animals found along the coast between Cape Frio and Cape St. Roque differed from or agreed with those inhabiting the more northern shore of the continent and the West Indian Islands. In the course of the following chapters I shall have occasion to return, more in detail, to this subject.—L. A.
[12]. Molinesia and Pœcilia.
[13]. This lecture was accompanied by careful descriptions and drawings on the blackboard, showing the structural differences between these groups. These are omitted, as they would have little interest for the general reader. The chief object in reporting these lectures is to show the aims which Mr. Agassiz placed before himself and his companions in laying out the work of the expedition, and these are made sufficiently clear without further scientific details.
[14]. As these investigations have been published with so much detail (Steenstrup, Alternate Generation, Sars’s Fauna Norwegica; L. Agassiz, Contr. to Nat. Hist. of U. S.), it has not been thought necessary to reproduce this part of the lecture here. Any one who cares to read a less technical account of these investigations than those originally published, will find it in “Methods of Study,” by L. Agassiz.
[16]. The winter palace of the Emperor.
[17]. Some weeks after this I chanced to ask a beautiful young Brazilian woman, recently married, whether she had ever been over this temporary road for the sake of seeing the picturesque scenery. “No,” she answered with perfect seriousness, “I am young and very happy, and I do not wish to die yet.” It was an amusing comment on the Brazilian estimate of the dangers attending the journey.
[18]. This road, which is but the beginning of railroad travel in Brazil, opens a rich prospect for scientific study. From this time forward the difficulty of transporting collections from the interior to the seaboard will be diminishing. Instead of the few small specimens of tropical vegetation now preserved in our museums, I hope that hereafter, in every school where geology and palæontology are taught, we shall have large stems and portions of trunks to show the structure of palms, tree-ferns, and the like,—trees which represent in modern times the ancient geological forests. The time is coming when our text-books of botany and zoölogy will lose their local, limited character, and present comprehensive pictures of Nature in all her phases. Then only will it be possible to make true and pertinent comparisons between the condition of the earth in former times and its present aspect under different zones and climates. To this day the fundamental principle guiding our identification of geological formations in different ages rests upon the assumption that each period has had one character throughout; whereas the progress of geology is daily pressing upon us the evidence that at each period different latitudes and different continents have always had their characteristic animals and plants, if not as diversified as now, at least varied enough to exclude the idea of uniformity. Not only do I look for a vast improvement in our collections with improved methods of travel and transportation in Brazil, but I hope that scientific journeys in the tropics will cease to be occasional events in the progress and civilization of nations, and will be as much within the reach of every student as journeys in the temperate zone have hitherto been. For further details respecting the building of this road, see Appendix No. IV.—L. A.