GENETICS IN SWEDEN 



BY 



Dr. NILS HERIBERT*NILSSON 



LECTURER. LUND 



THE SWEDISH SCHOOL OF EXPERIMENTAL GENETICS MADE 

 its start before the rediscovery of the Mendelian law. A preMendelian 

 geneticist, PEHR BOLIN, at that time assistant at the plant breeding institute 

 in Svalov, published in 1897 a paper dealing with artificial crosses between different 

 varieties of barley in Utsadesforeningens Tidskrift. He arrived at the conclusion 

 that no variation takes place in the first generation, while it does occur in the 

 second. This variation seems to follow definite laws, he says, as the resulting 

 varieties represent different combinations of parent characters. He has also found 

 that the variation in certain cases falls beyond the limits of the variation of the parent 

 plants. He knew the fact of combination, as did many of the pre*Mendelian 

 workers, but he did not push his knowledge to the point of exact numerical 

 relations. The value of BOON'S discovery does not seem to have been appreciated 

 at that time, and his name has not been mentioned in the foreign literature among 

 the pre*Mendelian workers, so fas as I know. This is explained by the circum* 

 stance that his paper is written in Swedish and published in a journal of applied 

 science. 



The first who made Mendel's discovery known in Sweden was the talented 

 plant physiologist in Lund, BENGT LIDFORSS. He had been much interested in the 

 mutation theory of HUGO DE VRIES, and he acquainted himself with Mendel's 

 discovery in that work. Mendel's discovery was considered as mainly a verifica* 

 tion of the mutation theory at that time, as it demonstrated in a clear way the 

 discontinuity and the constancy of the characters. He gave a masterly summary 

 of Mendel's discovery in a popular work published 1904. He had already at this 

 time investigations under way dealing with the problem of the origin of species 

 in the genus Rubus. He found that species originated through mutation as well 

 as through hybridization. Some species, as R. polyanthemus, gave rise to a great 

 number of morphologically different types when selfed, which formed an absolute 

 parallel to the mutations of DE VRIES in many cases. A still greater variation, 

 however, was obtained from the hybridization experiments. The hybrid caesius 

 X Wahlbergii, for instance, gave so great a variation in the second generation 

 that he was able to distinguish types among the descendants which resembled 

 nine species already described. There were additional types which did not resemble 

 any known species. These striking results led him to adopt the Mendelian point 

 of views more and more. He dismisses at last the mutation theory entirely and 

 holds the view that the seemingly spontaneous, wild forms represent the last 

 oscillations of a segregation. His discovery that in certain cases of successful 

 species crossing all the descendants resemble the female parent plant is very in* 

 teresting. The pollination stimulates the development of the ovules, according to 

 the explanation given by LIDFORSS, but does not bring about any nuclear fusions. 



