808 



SCIENCE. 



[N. S. Vol. XXIV. No. 625. 



teacher. He has thus been able to cut down 

 his text to 160 pages and to offer his book for 

 sale at a price corresponding to one cent per 

 page. The large number of figures for a book 

 of such small compass, shows that so far as 

 possible the training is to be through the eye, 

 and the identification of models and crystals 

 made easy. 



The order of treatment is by systems and 

 their subordinate classes, beginning with the 

 forms of highest symmetry; and the holo- 

 hedrism, hemihedrism and tetartohedrism of 

 forms is indicated, though made secondary. 

 The systems of nomenclature of Weiss, Nau- 

 mann and Miller are used side by side. The 

 relationships of the forms belonging to classes 

 within the same system are indicated by tables 

 and diagrams, in which the apparently holo- 

 hedral forms and those which bring out in 

 their development the real symmetry of the 

 group, are sharply differentiated. 



The six pages devoted to compound crystals 

 will seem to many inadequate, in view of the 

 great prominence of twins in the case of a 

 large number of species. Not the least valu- 

 able part of the work is an appendix giving a 

 tabular classification, which shows the sym- 

 metry elements and the simple forms of each 

 of the thirty-two classes of crystals. 



William Herbert Hobbs. 



SCIENTIFIC JOURNALS AND ARTICLES. 



The American Naturalist for November 

 contains three long papers : ' Variation in the 

 Number of Seeds of the (American) Lotus,' 

 by Kaymond Pearl ; * The Causes of Extinc- 

 tion of Mammalia,' by Henry F. Osborn; and 

 ' A Preliminary Study of the Finer Structure 

 of Areella,' by Joseph A. Cushman and 

 William P. Henderson. Professor Osborn's 

 paper, which is to be continued, discusses 

 seriatim the external causes, such as varia- 

 tions in climate, increasing cold, heat or mois- 

 ture, with their concomitant changes in plant 

 and insect life; and the relations of plants 

 and insects to mammals, with their bearing 

 on extinction. Discussion is desired and criti- 

 cisms and suggestions will be welcomed. 

 Messrs. Cushman and Henderson show that 

 the generally accepted idea of the structure 



of the test of Areella is incorrect, and that 

 the framework instead of consisting of simple 

 hexagons, touching one another at their sides, 

 consist of hexagons touching at their angles 

 and thus leaving triangular interspaces which 

 permit the interpolation of new columns of 

 hexagons as growth proceeds. There are many 

 ichthyological notes, while those relating to 

 botanical publications are, as usual, numerous. 



The American Museum Journal for October 

 is termed the Sponge Number, the principal 

 article being ' A Guide to the Sponge Alcove 

 in the American Museum of Natural History,' 

 by Roy W. Miner. This is well written and 

 well illustrated. Incidentally, it may be re- 

 marked that it is very difiicult to find in any 

 text-book a consecutive definition of a sponge; 

 we are told all about the structure and em- 

 bryology of sponges, but what a sponge really 

 is and its position in the animal kingdom has 

 to be gathered by much reading. The Journal 

 contains brief reports of several of the Mu- 

 seum expeditions, including those to Tahiti, 

 Colorado, North Carolina and East Africa. 



The Museum News of the Brooklyn Insti- 

 tute for December has articles dealing with 

 ' The Question of Common Names ' and, in 

 connection with a recently installed group, 

 ' The Golden Eagle, its Haunts and Habits.' 

 It is noted that the museum has acquired the 

 Ward collection of sponges and corals, the 

 former containing 150 specimens of siliceous 

 sponges and 660 of horny sponges; the latter 

 comprising 234 species of corals. The collec- 

 tion of sponges was brought together by the 

 late Professor Henry A. Ward and is ex- 

 tremely valuable from both the scientific and 

 the popular standpoint, comprising as it does 

 selected specimens from many years of collect- 

 ing. The leading article of the Children's 

 Museum section, under the title of ' General 

 and Mrs. Green,' deals with two bullfrogs 

 that have lived in the museum for four years. 



SOCIETIES AND ACADEMIES. 



THE AMERICAN PHYSICAL SOCIETY. 



The fall meeting of the Physical Society 

 was held in Chicago on December 1. In the 

 absence of President Barus, Past-president A. 



