AGASSIZ.

Engraved by J. Sartain from a Photograph.

OHN SARTAIN, whose work in mezzotint is deservedly famous, was born in London, October 24th, 1808. He came to the United States in 1830, and edited Sartain's Union Magazine from 1848 to 1852.

E

RELATIONS BETWEEN ANIMALS AND PLANTS AND THE SURROUNDING WORLD

VERY animal and plant stands in certain definite relations to

the surrounding world, some, however, like the domestic animals and cultivated plants, being capable of adapting themselves to various conditions more readily than others; but even this pliability is a characteristic feature. These relations are highly important in a systematic point of view, and deserve the most careful attention, on the part of naturalists. Yet, the direction zoological studies have taken since comparative anatomy and embryology began to absorb almost entirely the attention of naturalists, has been very unfavorable to the investigation of the habits of animals, in which their relations to one another and to the conditions under which they live are more especially exhibited. We have to go back to the authors of the preceding century for the most interesting accounts of the habits of animals, as among modern writers there are few who have devoted their chief attention to this subject. So little, indeed, is its importance now appreciated, that the students of this branch of natural history are hardly acknowledged as peers by their fellow investigators, the anatomists and physiologists, or the systematic zoölogists. And yet, without a thorough knowledge of the habits of animals, it will never be possible to ascertain with any degree of precision the true limits of all those species which descriptive zoölogists have of late admitted with so much confidence in their works. And after all, what does it matter to science that thousands of species more or less should be described and entered in our systems, if we know nothing about them? A very common defect of the works relating to the habits of animals has no doubt contributed to detract from their value and to turn the attention in other directions: their purely anecdotic character, or the circumstance that they are too frequently made the occasion for narrating personal adventures. Nevertheless, the importance of this kind of investigation can hardly be overrated; and it would be highly desirable that naturalists should turn again their attention that way, now that comparative anatomy and physiology, as well as embryology, may suggest so many new topics of inquiry, and the progress of physical geography has laid such a broad foundation for researches of this kind. Then we may

learn with more precision how far the species described from isolated specimens are founded in nature, or how far they may be only a particular stage of growth of other species; then we shall know, what is yet too little noticed, how extensive the range of variations is among animals, observed in their wild state, or rather how much individuality there is in each and all living beings. So marked, indeed, is this individuality in many families, and that of Turtles affords a striking example of this kind,- that correct descriptions of species can hardly be drawn from isolated specimens, as is constantly attempted to be done. I have seen hundreds of specimens of some of our Chelonians, among which there were not two identical. And truly, the limits of this variability constitute one of the most important characters of many species; and without precise information upon this point for every genus, it will never be possible to have a solid basis for the distinction of species. Some of the most perplexing questions in zoölogy and paleontology might long ago have been settled, had we had more precise information upon this point, and were it better known how unequal in this respect different groups of the animal kingdom are, when compared with one another. While the individuals of some species seem all different, and might be described as different species, if seen isolated or obtained from different regions, those of other species appear all as cast in one and the same mold. It must be, therefore, at once obvious, how different the results of the comparison of one fauna with another may be, if the species of one have been studied accurately for a long period by resident naturalists, and the other is known only from specimens collected by chance travelers; or, if the fossil representatives of one period are compared with living animals, without both faunas having first been revised according to the same standard.

Section XVI of essays on "Classification," complete.

THE

RELATIONS OF INDIVIDUALS TO ONE ANOTHER

HE relations in which individuals of the same species of animals stand to one another are not less determined and fixed than the relations of species to the surrounding elements, which we have thus far considered. The relations which individual animals bear to one another are of such a character, that