Page:Popular Science Monthly Volume 30.djvu/870

846 Among the many subjects treated of are relations of past faunas; origination of faunas; areas of specific, generic, family, and ordinal distribution; conditions effecting distribution; migrations of animals; dispersions; zoölogical regions accompanied by a colored outline-map; distribution of marine life; nature of marine faunas, such as deep-sea, oceanic, pelagic, littoral; succession of life; faunas of different geological periods; appearance and disappearance of species, reappearance, extinction, and other subjects dealt with from geological evidence. Here the author enters into interesting discussions in regard to possible reappearance of species, quoting opinions and statements from various authors, and leaning somewhat as to the possibility of a species evolving again from the parent or parallel stock. In reading these pages, one is more fully convinced than ever that such apparently inexplicable occurences of identical species in beds widely removed vertically are more rationally explained by the assumption of the very great imperfection of the geological record. As an evidence of this, consider the fact that over two hundred thousand species of insects have been described as living to-day. Now this class of creatures has been in existence since the Devonian, and probably as numerous in species since the Mesozoic as at the present day, and yet the number of fossil insects described from every geological horizon to the present would not exceed in number the species of the smallest order living at present. A species of Lingula, which is found in a few localities on the southern coast of the United States, if fossilized would very closely resemble certain forms in the Silurian. One might scan the Tertiary beds in the Southern States without finding a trace of this species, and yet an elevation of the coast-line of North Carolina might show this ancient worm in great numbers when the deposits below reveal no trace of it. This might appear to a future geologist like a re-evolution of this species, whereas, judging from what we know of the geographical limitations of certain groups, it can only be interpreted as the preservation of colonics under favorable conditions.

Globigeriua still survives, because the abysses of the deep sea probably remain in the same physical conditions as regards temperature, pressure, light, etc., as they did in the Cretaceous, and thus we have this creature and other cretaceous forms persisting to the present day.

We can heartily commend this book as a convenient and compact treatise on a great and voluminous subject.

The author of this work. Dr. Robert Bentley, is an eminent English botanist, who has had more than thirty years of practical experience as a teacher, and whose various text-books hold a first place in his own country. The present treatise is a model of clear, concise, and accurate statement, giving a complete popular view of the minute structures, the functions, and the development of the various organs of plants. Great pains have been taken by Professor Bentley to bring the different subjects treated of down to the present state of science, and much care has evidently been exercised in condensing the numerous details in each department and arranging them in the best manner for the pupil.

As physiological botany is the same in every part of the globe, and might exist in its fullness if there were only one species of plant in existence, the fact that this work is by an English author has no bearing upon its use in this country. The "Descriptive Botany," with its contained Flora, published two years ago in this series, and to which this is a sequel, covers all that portion of botanical science which has local bearings. In the introduction to that work, after explaining and enforcing the reasons for an early beginning of the study of plants by direct observation, it is recognized that physiological botany may be pursued with profit by ordinary school methods, and the publication of the present manual was accordingly promised; and it completes the exposition of botanical science in Appletons' series of science text-books.