BIOGRAPHICAL INDEX 



sion of such groups of fossils is always the same 

 in any vertical series of strata in which they 

 occur. 



Snell (or Snellius), Willebrord, ii, 119. Born at 

 Leyden, 1581; died Oct. 30, 1626. Dutch mathe- 

 matician. About the year 1621, while Professor 

 of Mathematics at Leyden, he discovered the law 

 of refraction. 



Spallanzani, Lazzaro, iv, 86. Born at Scandi- 

 ano in Modena, 1729; died in 1799. Remembered 

 chiefly for his discoveries and investigations in 

 the biological sciences. He refuted the evidence 

 of Needham that minute organisms form sponta- 

 neously in solutions of meat in water after boil- 

 ing, by demonstrating conclusively that if prop- 

 erly protected from the atmosphere no organism 

 will form. He discovered the function of the 

 ovum and spermatozoon, and demonstrated that 

 digestion is a chemical process by an ingenious 

 use of tubes filled with food introduced into the 

 stomach. 



Spencer, Herbert, iv, 268. Born at Derby, April 

 27, 1820; died at Brighton, Dec. 8, 1903. Eng- 

 lish philosopher, founder of the system known 

 as synthetic philosophy. He studied engineering 

 and during 1837-46 was employed as a railway 

 engineer. From 1846 he devoted himself to lit- 

 erary work, acting as sub-editor of the "Econo- 

 mist" from 1848 to 1853. In 1850 he published 

 "Social Statics"; and in 1855, "Principles of 

 Psychology." He began his "Synthetic Philoso- 

 phy" in 1860, completing it in 1896. He was in 

 sympathy and closely in touch with the work of 

 Darwin and Huxley, and in his writings he tried 

 "to express in a sweeping general formula the 



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