332 



SCIENCE. 



[Vol. XXII. No. 567 



colored fluorite in small cubic crystals is a common asso- 

 ciate of the telluride. The rocks of the district are 

 mostly granitic. The ores of high grade are successfully 

 worked by smelting, rather than by milling. 



Wm. P Blake. 



Haven, Conn. 



BOOK-EEVIEWS. 



A Pocket Key to the Birds of the Noithern United States. By 



A. C Apgak. Trenton, N. J., John L. Murphy. 50 p., 



50 cents. 



This small book, which can readily be carried in one's 

 pocket, gives a simple, usable key which will enable a 

 student of nature to determine the family and usually the 

 genera of any of our northern birds. It will be especia ly 

 valuable as a field book for one to carry in short 

 excursions. 

 The Soil in Relation to Health. By H. A. Milks, F. G. S., 



P. C. S., and E. Ckosket, D. P. H. New York, Macmillan 



& Co. 130 p., $1.10. 



As the result of the recent advance in matters of 

 hygiene many short accounts of the hygienic character- 

 istics of water and milk have been presented to the public. 

 The suggestion of soil in relation to health is a somewhat 

 new one. At the same time, it is perhaps as old as any in 

 general estimation, for every one has some conception that 

 certain kinds of soils are not healthful In this little 

 volume of 130 pages are collected ah of the general facts 

 known in relation to the hygiene of the soil. It is die- 

 cussed especially in connection with the subjects of the 

 water in the soil, the air in the soil and micro-organisms 

 in the soil. The relation of the soil in the distribution of 

 most important diseases is discussed, and the relation of 

 ground water to all phenomena of health is considered 

 carefully. In short, this little volume presents the factors 

 which should be considered in determining the healthful- 

 ness of any locality, so far as concerns its soil. 

 The Inadequacy of "Natural Selection." By Heebert Spencee. 



New York, D. Appleton & Co. 



In this little pamphlet have been republished the three 

 essays on the subject of Weismannism jjublished by Her- 

 bert Spencer in the Contemporary Review in 1893. These 

 trenchant criticisms of Weismann's theory are well known 

 and need no comment. In this form the essays form a 

 valuable addition to any library on the subject of recent 

 views of heredity. 

 The Native Calendar of Mexico and Central America : A 



Study in Linguistics and Symboli.'im. By Daniel G. 



Bkinton, M.D., LL.D. Philadelphia, David McKay. 



There is probably no question more imjjortant in 

 American archaeology, and none more obscure, than that 

 of the calendar in use by the natives of Mexico and Cen- 

 tral America before the Spanish conquest. Up to the 

 present time its solution has foiled every student, from 

 Humboldt down. 



In the essay before us the author does not take up the 

 mathematical and astronomical j)roblems involved, but 

 aims to define the geographical extension of the calendar, 

 its probable origin and its symbolic meaning. His re- 

 sults may be briefly stated. The same calendar system 

 is shown to have prevailed among all the semi-civilized 

 nations of Mexico and Central America ; its origin, he in- 

 clines to think, was among that branch of the Mayan 

 tribes which dwelt near the great ruins of Palenque and 

 Ocozingo, and built those cities; and it arose at first not 

 as a time-measure, but as a means of astrological divina- 

 tion, and only later was brought into relation to the luni- 

 solar year-counts of the tribes who adopted it. Its 

 essentially symbolic character is explained at considerable 

 length; and the etymology of the day and month names 



in the different languages is presented with greater full- 

 ness than has hitherto been attempted. 

 A Theory of Development and Heredity. By Heney B. Orr' 



Ph.D. New York, Macmillan & Co. 255 p. 



Any new presentation of the subject of heredity is wel- 

 come, for in recent years biological discussion has become 

 so intimately associated with this subject that there is a 

 general impression among students that no further ad- 

 vance along the lines of biological truth is possible until 

 this problem of heredity is in a measure solved. Prof. 

 Orr, of Tulane University, has endeavored to give us a 

 new view upon the subject of development and heredity. 

 His theory, while not absolutely new, perhaps, is certain- 

 ly fresh and novel in its applications, and in its associa- 

 tion of facts somewhat widely distinct and hitherto kept 

 separate. 



The theory of Prof. Orr has in it some of the features of 

 Weismann, inasmuch as it is based upon the supposed 

 continuity of germ jslasm, but differs radically from "Weis- 

 mann's theory in assuming the possible and, indeed, the 

 necessary modification of this germ plasm, by the condi- 

 tions surrounding the adult. The theory is in reality an 

 expansion of the old statement of Haeckel that heredity is 

 memorj'. The phenomena of heredity and development 

 are based by Prof. Orr wholly upon the nervous system of 

 organisms, and this nervous system he traces through the 

 lower organisms, and even extends it through the vegetable 

 kingdom, thus finding the essential features of the nervous 

 system co-existent with life. Heredity is habit; the germ 

 substance is continuous from generation to generation, 

 and its nervous factory remember. Great stress is placed 

 upon the known facts of the acquirement through habit of 

 reflex actions by the nervous system of the higher verte- 

 brates, and a similar action is supposed to be possessed in 

 all jjrotoplasm. The theory assumes that protoplasm, 

 like other matter, is extremely plastic and undergoes 

 physical or molecular modifications with every action of 

 the environment upon it. Acquired characters of the 

 adult affect all the protojjlasm oi the body, including the 

 germ plasm, and form thus the most important basis of 

 modification and development. The theory, in short, is an 

 attempt to show that heredity is due to slow modifications 

 of the nervous system of the germ plasm, produced upon 

 it by changed conditions, and applies equally to the body 

 protoplasm or the germ plasm. 



The view of Prof. Orr is suggestive, but it is doubtful 

 if it explains very much. If AVeismann's theory became 

 popular and sfiread all over the world rapidly because of 

 its simplicity and ready comprehension, it is safe to say 

 that Prof. Orr's theory will not have a like history. The 

 theory itself is a little more difficult to understand than it 

 is to understand heredity without it, for to explain every- 

 thing by a nervous system whose very presence is, in 

 lower organisms, a matter of hypothesis, does not advance 

 us very much on the line of simplicity. If Prof. Orr's 

 theory is true, it is certain that biologists are not ready 

 for it, because it relegates the whole subject of heredity 

 and develo23ment to that one branch of Isiology of which 

 we professedly know least, namely, that of mind. In spite 

 of this, the discussion of Prof. Orr is full of suggestion, 

 and will undoubtedly repay thorough reading and care- 

 ful thought on the part of any student of nature. 

 Method and Results. By Thomas H. Huxley. New York, 



D. Appleton & Co. 8vo., $1. 25. 



This book is the first of a series of nine bearing the 

 general title of "Collected Essays," in which Prof. Huxley 

 intends to gather together his scattered essays and ad- 

 dresses in a permanent form. One of the essays in this 

 volume relates to Descartes' "Discourse on Method," and 

 is designed to set forth Prof. Huxley's own views as to the 

 right method of scientific investigation ; while the other 



