The observations of T.H. Montgomery's (1901) and those of W.S. Sutton (1902) attained significance when T.
Boveri (1902) demonstrated in sea urchin, that different chromosomes of a set possess different qualities. He also showed, that presence of a complete set of chromosomes was important for survival. This observation derives support now from the fact that a hypodiploid (chromosome number <
2n) does not survive while a haploid individual may survive. It is also proved by the fact that trisomics involving different chromosomes differed morphologically as in case of
Datura and many other plant species and also in Humans (consult
Numerical Changes in Chromosomes and
Human Genetics).