THEORIES OF WEISMAXX AXD DE VRIES 401 



he has occupied the chair of zoology in that institution. He 

 has made his department famous, especially by his lectures 

 on the theory of descent. 



He is a forceful and interesting lecturer. One of his 

 hearers in 1896 wrote: "His lecture-room is always full, and 

 his popularity among his students fully equals his fame 

 among scientists." 



It is quite generally known that Weismann since he 

 reached the age of thirty has been afflicted with an eye- 

 trouble, but the inference sometimes made by those unac- 

 quainted with his work as an investigator, that he has been 

 obliged to forego practical work in the field in which he has 

 speculated, is wrong. At intervals his eyes have strengthened 

 so that he has been able to apply himself to microscopic 

 observations, and he has a distinguished record as an observer. 

 In embryology his studies on the development of the diptera, 

 and of the eggs of daphnid Crustacea, are well known, as are 

 also his observations on variations in butterflies and other 

 arthropods. 



He is an accomplished musician, and during the period 

 of his enforced inactivity in scientific work he found much 

 solace in playing "a good deal of music." ''His continuous 

 eye trouble must have been a terrible obstacle, but may have 

 been the prime cause of turning him to the theories with 

 which his name is connected." 



In a short autobiography published in The Lamp in 1903, 

 although written several years earlier, he gives a glimpse of 

 his family life. "During the ten years (1864-1874) of my 

 enforced inactivity and rest occurred my marriage with 

 Fraulein Marie Gruber, who became the mother of my 

 children and was my true companion for twenty years, until 

 her death. Of her now I think only with love and gratitude. 

 She was the one who, more than any one else, helped me 

 through the gloom of this period. She read much to me 

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