The International Scientific Series.— (Continued.} 



19. ANIMAL PARASITES AND MESSMATES. By Professor P. J. Van Ben- 



eden, University of Louvain. With 83 Illustrations. §1.50. 



20. FERMENTATION. By Professor P. Schutzenberger. With 28 Illustra- 



tions. $1.50. 



21. THE FIVE SENSES OF MAN. By Professor Julius Bernsteix, Univer- 



sity of Halle. With 91 Illustrations. $1.75. 



22. THE THEORY OF SOUND IN ITS RELATION TO MUSIC. By Pro- 



fessor Pietro Blaserna, Royal University of Rome. With numerous 

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23. STUDIES IN SPECTRUM ANALYSIS. By J. Norman Lockter, F. R. S. 



With 7 Photographic Illustrations of Spectra, and 52 other Illustrations. 

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24. A HISTORY OF THE GROWTH OF THE STEAM-ENGINE. By Pro- 



fessor R. H. Thurston, Cornell University. With 163 Illustrations. $2.50. 



25. EDUCATION AS A SCIENCE. By Alexander Bain, LL. D. $1.75. 



26. STUDENTS 1 TEXT-BOOK OF COLOR ; or, Modern Chromatics. With 



Applications to Art and Industry. By Professor Ogden N. Rood, Colum- 

 bia College. With 130 Illustrations. $2.00. 



27. THE HUMAN SPECIES. By Professor A. de Quatrefages, Museum of 



Natural History, Paris. $2.00. 



28. THE CRAYFISH : An Introduction to the Study of ZcSlogy.. By T. H. 



Huxley, F. R. S. With 82 Illustrations. $1.75. 



29. THE ATOMIC THEORY. By Professor A. Wurtz. Translated by E. 



Cleminshaw, F. C. S. With Illustrative Chart, $1.50. 



30. ANIMAL LIFE AS AFFECTED BY THE NATURAL CONDITIONS OF 



EXISTENCE. By Professor Karl Semper, University of Wiirzburg. 

 With 106 Illustrations and 2 Maps. $2.00. 



31. SIGHT : An Exposition of the Principles of Monocular and Binocular Vision. 



By Professor Joseph Le Conte, LL.D., University of California. With 

 132 Illustrations. $1.50. 



32. GENERAL PHYSIOLOGY OF MUSCLES AND NERVES. By Professor 



I. Rosenthal, University of Erlangen. With 75 Illustrations. $1.50. 



33. ILLUSIONS : A Psychological Study. By James Sullt. $1.50. 



34. THE SUN. By Professor C. A. Yocjng, College of New Jersey. With 83 



Blustrations. $2.00. 



35. VOLCANOES ; What they Are and What they Teach. By Professor John 



W. Judd, F. R S., Royal School of Mines. With 96 Illustrations. $2.00. 



36. SUICIDE : An Essay in Comparative Moral Statistics. By Professor Henry 



Morselli, M. D., Royal University, Turin. With 4 Statistical Maps. 

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37. THE FORMATION OF VEGETABLE MOULD, THROUGH THE AC- 



TION OF WORMS. With Observations on their Habits. By Charles 

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