768 



SCIENCE 



[N. S. Vol. XXX. No. 778 



All of the classes of invertebrates found 

 fossil are described in more or less detail ac- 

 cording to the prominence of the classes. 

 These are taken up first in a general way to 

 acquaint the student with the hard parts and 

 the relation of the soft parts to them. The 

 orders and suborders adopted are up to date 

 and these are next concisely described, but no 

 further classification is offered, nor are the 

 genera, even the common genera, defined. 

 The various groups are illustrated by a few 

 well-selected forms and these are carefully de- 

 scribed in the legend as to the source whence 

 obtained, the name of the animal, locality and 

 formation, order or family and the symbols 

 referring to the detailed structures. 



Most of the classes are adequately treated 

 for an elementary work, but a few are handled 

 too briefly to give a proper conception of their 

 intricacy. For instance, the crinoids are de- 

 scribed in nine pages and the horde of Camer- 

 ata in one, the Hydrophorida or Cystidea 

 proper in four, the starfishes and ophiurids 

 each in three, and the varied and very impor- 

 tant Paleozoic trilobites in six. American 

 paleontologists will be also disappointed to 

 see the Trepostomata Bryozoa still ranged 

 among the tabulate corals. 



Charles Schuchert 



Yale Univebsitt 



Light. By Richard C. Maclaurin, President 

 of the Massachusetts Institute of Technol- 

 ogy. New York, published by the Columbia 

 University Press. 1909. 

 A popular exposition of selected topics, be- 

 ing the Jesup lectures delivered at the Amer- 

 ican Museum of Natural History during the 

 winter of 1908-9. This book, while not com- 

 prehensive enough to serve as a text-book, will 

 meet the requirements of those who wish to 

 acquaint themselves with the experimental 

 part of the work that has given us our modern 

 theory of light. The subjects are treated in 

 the following order: (1) Early Contributions 

 to Optical Theory, (2) Color Vision and Color 

 Photography, (3) Dispersion and Absorption, 

 (4) Spectroscopy, (5) Polarization, (6) The 

 Laws of Reflection and Refraction, (7) The 



Principle of Interference, (8) Crystals, (9) 

 Diffraction, (10) Light and Electricity. The 

 author's standing as a physicist is a sufficient 

 guarantee that the book is free from errors, 

 and the subject is treated in a very readable 

 manner, free from mathematics and requiring 

 little or no previous knowledge of the subject 

 on the part of the reader. It brings the sub- 

 ject down to date, or as much so as can be 

 expected in a popular treatment. 



R. W. Wood 



RECENT VIEWS OF L. CVENOT ON THE 

 ORIGIN OF SPECIES BY MUTATION '^ 

 The results obtained in the study of varia- 

 tion from the point of view of its origin, of 

 its morphological significance and of the in- 

 tegral transmission of mutations as opposed 

 to fluctuations, could not but exert a profound 

 influence on the hypotheses that have been 

 brought forward to explain evolution. It is of 

 particular interest to compare these results 

 with the classic theories of Lamarck and Dar- 

 win. Primarily, these are attempts to account 

 for the phenomena of adaptation: Lamarck 

 invokes use and disuse, effort and habit, and 

 considers their effects as directly adaptive and 

 hereditary; thus he explains the evolution of 

 organs necessary for life in certain surround- 

 ings and the regression of those that are use- 

 less under an animal's particular environ- 

 mental conditions. 



Darwin, while admitting the effects of use 

 and disuse, emphasizes above all the selection 

 of minute fluctuating variations, favorable in 

 the struggle for existence, and thus he ex- 

 plains morphological changes and the final 

 perfection of adaptation in an organ as the 

 result of a slow and continuous progress. 



To be sure, the sudden appearance of cer- 

 tain mutations, transmissible in their entirety, 

 and the instability of fluctuating variations, 

 are factors not at all in accord with Lamarck's 

 attempted explanation, nor with that of Dar- 

 win; but perhaps there are no longer many 



' Cugnot, L., 1908, " Les Idges Nouvelles sur 

 rOrigine des Esp6ees par Mutation." Translated 

 from Rev. g4n. Sei. pures et appliq., Ann. 19, no. 

 21, 15 nov., 1908. 



