Part 70

Museums of Natural History or “Cabinets of Natural Curios” as they were sometimes called, were established in the first half of the nineteenth century in connection with the various natural history societies. These were of much service in stimulating the collection of zoological “specimens” and in arousing a popular interest in natural history.

The zoological museum of earlier days consisted of rows on rows of systematically arranged specimens, each carefully labelled with scientific name, locality, date of collection and donor—much like the pages of a catalogue. All this has now been changed; the bottles of specimens have been relegated to the storeroom, and the great plate glass cases of the modern museum represent individual studies in the various fields of modern zoological research, or individual chapters in the latest biological text-books. Often the talent of the artist and the skill of the taxidermist are cunningly combined to produce most realistic bits of nature.

The United States National Museum, the American Museum of Natural History, the Field Columbian Museum and the Museum of Comparative Zoology are among the finest museums of the world, while many of the states, cities, and universities maintain public museums as a part of their educational systems.

Systematic Zoology and Taxonomy.

The work in systematic zoology is now mainly carried on by specialists in relatively small groups of animals. This is necessitated both by the increasingly large number of species known to science and by the completeness and exactness with which species must now be defined. The majority of systematic workers are now connected with museums where the large collections furnish material for comparative studies.

Prominent in this field is the United States National Museum, the publications of which are mainly taxonomic and zoogeographic, and cover every group of organism. The adequacy of this great museum for such studies may be illustrated by the collection of mammals. This museum has the types of 1135 of the 2138 forms (including species and subspecies) of North American mammals recognized in Miller’s list, and less than 200 forms lack representatives among the 120,000 specimens of mammals. Systematic monographs of several of the orders of mammals have been published.

Systematic study of the birds has brought the number of species and subspecies known to inhabit North and Middle America to above 3000. The most comprehensive systematic treatise is the still incomplete report of Ridgeway of which seven large volumes have already been issued.

On the reptiles, the most complete monograph is that by Cope entitled “The Crocodilians, Lizards and Snakes of North America.”

The Amphibia have also been studied by Cope, whose report on the Batrachia of North America is the standard taxonomic work.

The most comprehensive systematic work on fishes is the “Descriptive Catalogue of the Fishes of North and Middle America” by Jordan and Evermann.

The invertebrate groups have been in part similarly monographed by the members of the U. S. National Museum staff and others, and further studies are in progress. Other taxonomic monographs published by this museum include the various groups of animals from many different parts of the world.

A number of the larger State, municipal, and university museums publish bulletins on special groups represented in their collections as well as articles of general zoological interest.

Expeditions, subsidized by museum and private funds, are from time to time sent to various parts of the world and their results are often published in sumptuous manner.

The total number of living species of animals is unknown, but considering that about a quarter of a million new species have been described during the past thirty years, it is probable that several million species are in existence to-day. More than half a million have been described. These are probably but a small fraction of the number that have existed in past geological ages.

Thus, in spite of all the work that has been done in systematic zoology and as the number of known species continues to increase, there still remain many groups of animals, some of which are by no means rare or minute, in which probably only a small proportion of the species are as yet capable of identification.

It is only since the publication of Ward and Whipple’s “Fresh-water Biology” within the past year that the amateur zoologist could hope to find even the names of all the organisms which may be collected from a single pool of water. And in many cases he will still meet with disappointment, for many of our protozoa and other fresh-water organisms have not yet been described as species.

During the past few years there has been a tendency on the part of some of our biologists engaged in experimental work to disparage the studies of the systematists. It must be granted, however, that both lines of work are essential to the sound development of zoological science, for experimental investigations in which the accurate diagnosis of species is ignored always result in confusion.

Ecology.—The marvelous modifications in structure and instincts by which the various animals are adapted to their surroundings now forms a special topic in biological research and one of the most fascinating. The adaptations in habitat, time, behavior, appearance and even in structure are found capable of a certain individual modification when studied experimentally.

Zoogeography.—Closely associated with systematic zoology, and indeed a part of the subject in its broader sense, is the study of the geographical distribution of animal species and larger groups.

Paleontology.—The geological succession of organisms embraces a field where zoologist and geologist meet. The wonderful progress made by American investigators is well described in the preceding chapters on Historical Geology and Vertebrate Paleontology.

Biometry.

Since Darwin’s theory of evolution postulated the origin of new species by means of natural selection, it was obviously necessary in order to apply a critical test to determine the precise limits of a species. It was, therefore, proposed to subject a given species to a strict examination by the application of statistical methods to determine the range of variation of its members and the extent to which the species intergrades with others. Other problems, particularly those concerning heredity, were treated in similar manner. This branch of biological science was particularly developed by the English School, led by Sir Francis Galton, followed by Karl Pearson and William Bateson.

In America the methods of biometry have been utilized extensively by Charles B. Davenport, Raymond Pearl, H. S. Jennings and others in the solution of problems in genetics and evolution. Their work shows the great value of critical statistical analysis in the interpretation of biological data. A thorough training in mathematics is now found to be hardly less important for the biologist than is a knowledge of physics and chemistry, for the science of biometry has become one of the most important adjuncts to the study of genetics.

Comparative Anatomy and Embryology.

Comparative Anatomy.—Upon the foundations laid down by Cuvier a century ago the present elaborate structure of comparative anatomy of animals, both vertebrate and invertebrate, has been developed. Vast as is the present accumulation of facts and theories many important problems still await their solution. Jeffries Wyman was long a leader in this field, where many workers are now engaged.

Embryology.—The embryological studies, so brilliantly begun by Von Baer early in the nineteenth century, are still in progress. They have now been extended to the groups more difficult of investigation and into the earliest stages of fertilization and implantation in the mammals. Artificial cultural methods have yielded important results. Louis and Alexander Agassiz, Mark, Minot, Brooks, Whitman, Conklin and E. B. Wilson have taken prominent parts in this work.

In the early nineties embryological studies were directed to the arrangement of cells in the dividing egg, and there was much discussion of “cell lineage” in development. Valuable as were these studies they threw comparatively little light on the general problems of evolution.

Experimental Embryology.—A more fertile field, developed at the same period and a little later, was found in experimental embryology. The discoveries made by Driesch and others in shaking apart the cells of the dividing egg or by destroying one or more of these cells gave a new insight into the potency of cells for compensatory and regenerative processes. These studies attracted many able investigators, who made still further advance by subjecting the germ cells, developing eggs, embryos, and developing organs to a great variety of artificial conditions.