Page:Popular Science Monthly Volume 8.djvu/774

754 presented in any other light, unless it were given as a bare descriptive catalogue of details.

With each group (considered as a special study) are given a brief sketch of the structure and habits of some of its leading forms, their affinities, embryology, and a very useful table of the literature of the subject. A list of the authors referred to indicates clearly how few Americans have contributed to a knowledge of the subject.

The advanced character of the work is seen in the adoption of Haeckel's terms for different conditions of the embryo, such as the morula stage, planula stage, gastrula stage, etc. The ascidian stage is also recognized in the development of Vertebrata. Amphioxus is considered separately from the fishes, the Brachiopoda are placed among the worms. Altogether it forms one of the most valuable works of science yet published in this country, and it is safe to say that no working naturalist can do without it.

As a second edition of the work must soon be demanded, we trust it may be accompanied by a table of contents.

is a reprint from Major J. W. Powell's report of his explorations of the Colorado River, giving a full scientific account of the little animals known on the Western prairies as Pocket Gophers. Regarding the two genera Geomys and Thomomys as constituting a perfectly natural group of the grade of a family, Geomyidœ, the author describes them as "among the heaviest for their inches of any animals in this country, of squat, bunchy shape, with short, thick limbs, a short tail, very small or rudimentary ears, small eyes, no appreciable neck, and thick, blunt head; and they are as completely subterranean as the mole itself. They are rarely or momentarily seen above the ground; they excavate endless galleries in the earth in their search for food, frequently coming to the surface to throw out the earth in heaps, but plugging up these orifices as soon as they have served their purpose."

Geomys contains five (some authors say seven) well-defined species; Thomomys but a single species, including three recognizable races, out of which, by the process of species-mongering so common with earlier naturalists, a dozen separate species were made. While in Geomys the links have disappeared and the species are well-pronounced, in Thomomys the separation is incomplete, and the connecting forms still visible. "The genus appears to be working into a number of species, but the process is still far from completion." Adopting modern philosophical views, the author's tendency is to reduce the number of species, seeing only races or varieties where others claim to have found well-defined species. The several species constituting the family are separately described. The cranial and dental characters of the group are afterward treated, and the work closes with a further description, communicated by Prof. G. Brown Goode, of Geomys tuza, a form confined to Florida, Alabama, and Georgia, and there known as Salamanders.

Prof. Coues has the rare faculty of making even technical descriptions interesting, and for this reason the work commends itself to the attention of other than scientific readers.

the preface to this little book the author tells us that it is intended for beginners in the use of the microscope, a purpose that appears to have been kept well in mind in the subsequent pages, as the explanations are clear, the directions explicit and suitably detailed; and nothing has been attempted that lies beyond the understanding of any intelligent girl or boy of fifteen. After pointing out the numerous applications of the instrument, that are every day extending, the simple and compound microscope, and the essential parts of each, are described. The various forms in use are next enumerated, with brief descriptions of the most noted; and then follow practical directions for the selection of a microscope, and the requisite accessory apparatus. Illumination, the manipulation and care of the instrument, and the