434 A CENTURY OF SCIENCE 



the food supply by suitable protection and artificial 

 propagation. The work includes also edible and other- 

 wise useful mollusks and Crustacea. Their marine and 

 fresh-water laboratories have also been of great service 

 to general biological science. 



Economic Ornithology and Mammalogy. In addition 

 to the local bird clubs and the American Ornithologists 

 Union for the study and preservation of bird and mam- 

 mal life, the Bureau of Biological Survey has for some 

 years conducted investigations on the economic import- 

 ance of the various species. The publications of this 

 Bureau are of great value both in determining the 

 economic status of our birds and mammals, and also in 

 recommending means for the protection of the beneficial 

 species and the destruction of the injurious. Several of 

 the States issue similar publications. 



Genetics. 



One of the most interesting chapters in biology relates 

 to the development of the modern science of heredity, 

 or genetics. 



Previous to the year 1900, when the Mendelian princi- 

 ple of inheritance was re-discovered, the relative import- 

 ance of heredity and of environment in the development 

 of an organism was little understood. It is true that 

 Weismann had insisted on the independence of soma and 

 germplasm some years earlier (1883), but the body of, 

 the individual was still generally considered the key to 

 its inheritance. 



The recognition of the general application of Mendel's 

 discovery gave a great impetus to experimental breeding 

 both in plants and animals. While heretofore it had been 

 necessary to depend upon the somatic characters as evi- 

 dence of the hereditary constitution of an individual, it 

 now became possible, knowing the hereditary constitution 

 of the parents of any pair of individuals, to predict with 

 almost mathematical certainty the characters of their 

 possible offspring. 



In general, the laws of possible chance combinations of 

 any group of characters determine the probability of any 

 particular offspring possessing one or many of those 



