DEPARTMENT OF EXPERIMENTAL EVOLUTION * 



C. B. Davenport, Director. 



Certain portions of that unending stream of reproductive matter which has 

 come down to us from the time when Hfe began on earth and by changes in 

 which all evolution has taken place are now under our careful observation and 

 to a large extent under our control. It is the business of the Department of 

 Experimental Evolution to study the behavior of this germ-plasm and to note 

 its reaction to the conditions we impose. 



At present our index of the qualities of any germ-plasm is the collection of 

 characteristics shown by the individuals (somas) that arise from it. Each 

 soma is the biological analysis of its germ-plasm. The breeder as he exam- 

 ines his produce selects blood lines or strains on the basis of that produce. 

 And in nature, by the acceptance or rejection of particular individuals, any 

 peculiarities that arise in the germ-plasm are preserved or destroyed. 



As just stated, evolution consists of changes in the germ-plasm. These 

 changes are chemically appreciable, for, as Reichert and Brown f have shown, 

 the haemoglobins of different genera of mammals crystallize in a characteristic 

 manner, and T. B. Osborne has demonstrated! that the proteins of various 

 grains are chemically unlike. These changes are biologically appreciable in 

 the variations of the somas that result. Formerly it was held that the germ- 

 plasm is undergoing a slow change and by a selection of streams varying in 

 the right manner we might, in the course of time, build up a new and favor- 

 able characteristic. To-day a hopeful hypothesis is that changes occur in the 

 germ-plasm suddenly and in large amount, so that each results in a new char- 

 acteristic. 



While the soma is for us the analysis of the germ-plasm we are studying, 

 we have to recognize that this analysis is subject to certain errors. Of these 

 one of the most difficult to eliminate is the error of variation of the soma 

 under different environmental conditions. This is the "ontogenetic varia- 

 tion" of certain authors and the "fluctuation" of others. Current hypothesis 

 is that fluctuations are not indicative of the constitution of the germ-plasm, 

 but only of the external conditions in which the soma has developed ; but this 

 hypothesis is too simple, for external conditions do not produce always the 



* Address : Cold Spring Harbor, Long Island, New York. Grant No. 478. $28,200 

 for investigations and maintenance. (For previous reports see Year Books Nos. 3, 4, 

 5, and 6.) 



t E. T. Reichert and A. P. Brown : The crystallography of hemoglobins. Proc. Soc. 

 Exper. Biol, and Med., v, pp. 66-68. 



t Amer. Jour, of Physiology, 1906-07. 



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