530 VARIATIONS 



red flowers may become associated with white flowers, and in 

 crossing varieties of Corn the purple aleuron layer commonly 

 associated with starchy endosperm may become associated with 

 waxy endosperm, thus resulting in unusual combinations of 

 characters. 



Sometimes, due to irregularities in cell division, ofifspring 

 appear with more chromosomes than their parents and this may 

 be responsible for much variation in characters. Many mutants 

 have more chromosomes than the normal type from which they 

 arose. One of the mutants, gigas, of Lamarck's Evening Prim- 

 rose has twice as many chromosomes as the normal type. 



About a quarter of a century ago, August Weismann, (1834- 

 1914), a German biologist, proposed the theory that plants and 

 animals consist of two kinds of protoplasm, only one of which is re- 

 sponsible for the origin of hereditary variations. The protoplasm 

 of which sperms and eggs are formed he called germ-plasm, and all 

 protoplasm that does not have to do directly with forming sex 

 cells he called somatoplasm. Thus the protoplasm of all vegeta- 

 tive structures of plants, such as leaves, roots, and stems is 

 somatoplasm. Even the protoplasm in the parts of a flower, 

 excepting the protoplasm immediately involved in the production 

 of sex cells, is somatoplasm. According to Weismann, the 

 characters of a species are determined by certain units or factors 

 within the germ-plaem and these factors are organized chromatin 

 bodies, probably the chromatin granules one sees when a nucleus 

 is magnified. In each plant or animal these factors are numerous, 

 one for each character, and they have the power to grow and 

 divide. In the numerous cell divisions, by which an individual 

 develops from a fertilized egg to maturity, these factors undergo 

 division and distribution, so that in the cells of every organ of an 

 individual there are present the factors for producing the char- 

 acters of the organ. Thus the fertilized egg, which is the germ- 

 plasm the individual inherited from its parents, is responsible for 

 the body of the individual as well as for the germ-plasm the 

 individual transmits to the next generation. The somatoplasm 

 is formed from the germ-plasm and it protects and feeds the germ- 

 plasm which Weismann regarded as distinct from the somatoplasm 

 and as passing from generation to generation in the form of 

 sperms and eggs without having its factors materially changed by 

 the modifications of the somatoplasm of the individuals of each 



