THEORIES OF WEISMANN AND DE VRIES  qor 
he has occupied the chair of zodlogy 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 cve- 
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 eves 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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