June 25, 1915] 



SCIENCE 



ei9 



far as philosophical views of nature were concerned 

 I was a blank sheet of paper, a tabula rasa. I 

 read the book ["Origin of Species"] first in 1861 

 at a single sitting {sic) and with ever-growing en- 

 thusiasm. When I had finished I stood firm on the 

 basis of the evolution theory, and I have never seen 

 reason to forsake it. 



With just pride he mentions the fact that 

 he was one of the first scientific men in Ger- 

 many to defend publicly Darwin's theory; 

 Fritz Miiller was the first to publish a work 

 in favor of that theory ("Fiir Darwin," 

 1864), Haeekel was the second ("Generelle 

 Morphologic," 1866) and Weismann was 

 the third, his inaugural address at Freiburg 

 on the "Justification of the Darwinian 

 Theory" ("Ueber die Bereehtigung der 

 ■ Darwin 'schen Theorie") being published 

 in 1868. 



Thereafter his contributions to the Dar- 

 winian theory were numerous and impor- 

 tant. They appeared from 1872 to 1902 as 

 a series of books and contributions. Five of 

 these earlier contributions were translated 

 into English by K. Meldola and were pub- 

 lished as two large volumes in 1882, with an 

 introduction by Charles Darwin. Subse- 

 quent studies on evolution were so inti- 

 mately associated with his theories of hered- 

 ity that they can best be considered under 

 that topic. 



Weismann 's contributions to biological 

 theory were so extensive and important that 

 they overshadow to a great extent his ob- 

 servational and experimental work, and yet 

 the latter was by no means small or unim- 

 portant. Among these observational and 

 experimental studies must be mentioned 

 especially his extensive works on "The 

 Development of Diptera" (1865), "Nat- 

 ural History of the Daphnoidea" (1876- 

 79), "Origin of the Sex Cells of the 

 Hydromedusffi" (1883), "Seasonal Di- 

 morphism of Butterflies" (1875), "Origin 

 of Markings of Caterpillars" (1876) and 



"Transformation of the Mexican Axolotl 

 into Aniblystoma.^' 



Some of his earlier work was done with- 

 out assistance, but in all of his later obser- 

 vational and experimental studies he had 

 the assistance of his wife or other helpers. 

 Much of his work was doue in collaboration 

 with some of his students or assistants. His 

 method of work was to a large extent forced 

 upon him by his eye affliction. After 1864 

 all reading had to be done for him, at first 

 by his wife and after her death by a secre- 

 tary. Experimental work was done under 

 his supervision by his assistant and janitor. 

 All microscopic work was done by his 

 pupils, to whom he suggested topics and 

 whose work he supervised daily. These 

 theses were always in direct relation to his 

 theories and to that phase of them which 

 interested him most at the moment. 



But valuable as much of his observational 

 and experimental work was, there is no 

 doubt that he will be remembered chiefly 

 for his theories of heredity. His earliest 

 writings on this subject date from the year 

 1883 and his latest were published but a 

 few years before his death. His "Essays 

 upon Heredity and Kindred Biological 

 Topics" were translated into English and 

 published in two volumes in 1889 and 1892. 

 Probably his most important work on this 

 subject is his book entitled "The Germ- 

 Plasm, A Theory of Heredity" which was 

 published in English in 1893. Subsequent 

 worlcs on heredity are ' ' On Germinal Selec- 

 tion" (1896) and "Vortrage iiber Descen- 

 denztheorie" (1902). This last-named 

 work, which was published in English 

 under the title "The Evolution Theory" 

 (1904), consists of a summary and an ex- 

 pansion of many of his previous writings 

 on the subjects of evolution and heredity; 

 indeed, as he says in the preface of this 

 book, it is "a mirror of the course of my 

 own intellectvial evolution." 



