chorda tympani then passes directly forward beneath the spiracular cleft and close to its ventral edge. It soon turns inward and passes a considerable distance nearly parallel with the anterior wall of the cleft. Near the rudiment of the tongue it meets and fuses with the lingual brach of the trigeminus.

At this stage of the embryonic development of Microtus, therefore, the primitive continuity of the epithelium of the spiracular cleft and the skin still persists, and the chorda tympani passes behind and underneath the cleft and unites in a typical manner with the lingual nerve.

Third Embryo.

In the oldest of the three embryos, from which projections were made as from the second embryo, the pinna has begun to form, the mandibular and hyoid arches no longer appear as viscerial arches and have assumed in a general way the adult conditions. The skeletal regions are still for the most part filled with mesenchyme cells, but the fundaments of MECKEL'S cartilage and of the hyoid cartilage are distinguishable.

The Spiracular Cleft and External Auditory Meatus.The comparatively large orifice of the external auditory meatus is bordered by the ridges or fundaments of the pinna. The meatus soon narrows into a flattened cavity with its shortest diameter lying in the dorso-ventral plane, as seen in sagittal section. Its course is in a cephalo-ventral direction. It terminates as a blind tube. In a plane about .075 mm. outward from the blind end of the external auditory meatus, and dorsal of the meatus at a distance about equal to the greatest diameter of the meatus at this region, lies the blind end of the cleft which in the second embryo was identified as the spiracular. This cleft is also a flattened cavity with its longest diameter, as seen in sagittal section, lying in nearly the horizontal plane. It passes inward for a short distance, then takes a cephalo-ventral direction and opens into the pharynx. It is an important fact that in this embryo there is no continuity between the epithelium of the spiracular cleft and the skin.

The Chorda Tympani.—The ganglia and the main trunks

of the nerves are essentially the same as described for the second embryo. In addition to the inferior dental and lingual branches of the submaxillary, the mylo-hyoid and masseter branches are clearly defined. The lingual occupies a position along the inner side of MECKEL'S cartilage and can be traced forward into the lateral region of the tongue. Of the facial nerve, also, the supra-maxillary and auriculo-temporal are easily traced in their usual positions. The chorda tympani is easily traced from its point of origin from the facial trunk. It passes behind MECKEL's cartilage, takes the same general direction that it does in the earlier embryo, and joins the lingual nerve near the point of separation of the latter from the inferior dental. But the relation of the chorda tympani to the spiracular cleft is distinctly different from that found in the earlier embryo. In its course in front of the hyoid cartilage and behind the proximal end of MECKEL'S cartilage, it passes over the extreme lateral end of the spiracular cleft and close to its dorsal edge. It remains a question whether this lateral end of the spiracular cleft is the primary end of the cleft or a secondary evagination from it. It might be the latter, since it is generally accepted that the closed end of the ceft by evagination outward towards the external auditory meatus and upward around the chorda tympani and auditory ossicles, forms the tympanic cavity of the adult.

We find, then, at this stage of development that the chorda tympani no longer lies underneath the spiracular cleft but that it passes over the closed end of the cleft, or over the fundament of the tympanum. This is the morphological position the nerve holds in the adult.

Conclusions.

The results of this study of the embryological development of the chorda tympani in Microtus lead to the following conclusions:

1. In the earlier stages of development the chorda tympani passes behind and underneath the spiracular cleft. 2. In

later stages this nerve occupies a position over and in front of the closed end of the spiracular cleft which is generally accepted to be the fundament of the tympanum. 3. The chorda tympani is, therefore, a post-spiracular nerve, and is to be considered as the homologue of a post-trematic nerve of fishes and amphibians.

EDITORIAL.

NATURE STUDY.

Energetic, enthusiastic and intelligent efforts are being made to introduce Nature Study into the American public school curriculum. The efforts themselves are not new, but enthusiasm and intelligence in connection with them perhaps are. HUXLEY'S insistence upon the use of that which is vitally and practically related to human activities rather than conventional hereditary materials for the purposes of educational training, and AGASSIZ's pleas for the study of Nature before books are giving evidence of their influence.

With the year 1905 there will appear a journal devoted to Nature Study in the elementary schools. The founding of this, the Nature Study Review, is encouraging evidence of the recognition of the place and values of the study of Nature in our schools, and of the active interest of scientifically trained men. The editorial committee of the Review consists of L. H. BAILEY of Cornell University, H. W. FAIRBANKS of Berkeley, California, C. F. HODGE of Clark University, J. F. WOODHULL and M. A. BIGELOW of Teacher's College, New York City. These men, and such as they, are intelligently introducing the materials of natural science into our public schools. They are effecting just the kind of utilization of the materials of their own sciences that HUXLEY devoted so much of his energy and enthusiasm to encouraging. Grounded in genuine interest in scientific work as a source of knowledge which will promote the progress of the race, they are reaching beyond the narrowly circumscribed sphere of scientific investigation with the purpose of making Nature contribute directly to the education which is an important condition of human happiness and efficiency.

Perhaps no other book so well voices the judgment of those who stand close to the American school system as HODGE'S Nature Study and Life.' It is a book which reveals the nature lover as well as the trained scientist in its author. It presents a sensible, highly practical scheme for the study of animals and plants in the graded school, while at the same time filling the reader with faith in the possibilities of the work for training, and with enthusiasm for Nature Study. Enter into the spirit of the life about you; do not live to search for truth, no matter what kind, but search for knowledge, understanding and sympathetic appreciation of Nature in order that life may be fuller, freer, and more nearly perfect- this is the injunction of the book. Learn to know the living beings as thoroughly as does the scientist, and to love and sympathize with them as he too often does not. There is inspiration for the reader in this book, for the author's faith in his cause and his enthusiasm are contagious. No one should read it who does not care to have his interest in Nature Study, both in and for itself and as a means of training the child, greatly increased.

Great depth of insight into the significance of the signs of the times in natural science is not necessary in order that one should be able to say that the next generation of Americans is to be a generation of naturalists. Interest in Nature is rapidly increasing and the introduction of Nature Study in the schools is now going to equip our future scientific specialists with an intimacy of acquaintance and sympathetic appreciation of Nature that will enable them to live the better and enter the more fully into the truth of their subjects. The important thing is that this general interest in Nature Study be made to contribute truly earnest investigators rather than dilettanti.

The study of animal behavior, of the life-histories, habits, instincts, and intelligence of organisms, of their relations to human industries, is only a small part of Nature Study, to be sure, but for those of us whose interests center about the func

1 C. F. HODGE. Nature Study and Life. Ginn & Company, Boston, 1902. $1.50.