THEORIES OF WEISMANN AND DE VRIES 407 



zoology, until his retirement a few years before his death. 

 He has made his department famous, especially by his lec- 

 tures on the theory of descent. 



He was 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 was afflicted with an eye- trouble, but the 

 inference sometimes made by those unacquainted with 

 his work as an investigator, that he was obHged to forego 

 practical work in the field in which he speculated, is wrong. 

 At intervals his eyes strengthened so that he was 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 was 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 



