386 C. H. DANFORTH 



The choice of a method of procedure presents a number of 

 difficulties. Attempts to bring special influences to bear on 

 cells within the living body are attended by many uncertainties 

 and, on the other hand, the treatment of suitable germ cells 

 outside the body in most cases requires the development of a 

 special and diffictilt technique. The desideratum would seem 

 to be the possession of a means of administering definite amounts 

 of reagents to the germ cells without otherwise disturbing their 

 normal environment. Despite the fact that it does not lend 

 itself readily to quantitative investigations, the inhalation method 

 devised by Stockard seems to be the most satisfactory tjius 

 far employed. A considerable number of reagents are suitable 

 for use by this method, but ethyl alcohol is the one that has 

 been most completely tested (Stockard, '13; Cole and Davis, '14; 

 Stockard and Papanicolaou, '16; Nice, '17; Pearl, '17^. For 

 these reasons ethyl alcohol administered by the inhalation 

 method was employed in the experiments reported in this 

 paper. 



Pearl ('17) has interpreted results obtained by himself and 

 others as indicating that inhaled alcohol affects germ cells dif- 

 ferently according to their vitality, destroying some, injur- 

 ing some permanently, and producing no more than a tran- 

 sient effect on others. In the case of the fowl, he believes that 

 practically maximum treatment with alcohol and certain other 

 vapors results in an elimination of weaker germs with a con- 

 sequent rise in the average vigor of the chicks actually pro- 

 duced. In other words, treating the parent with alcohol vapor 

 results in a selection of germs in favor of those which produce 

 the most vigorous young. It was not shown in his experiments 

 that any characteristics other than those dependent on general 

 vigor were affected by the treatment, the Mendelian ratios for 

 the few characters involved being essentially the same in both 

 experiment and control. 



At the time when Pearl's papers appeared the writer was just 

 concluding a breeding experiment with poultry in which several 



1 An extended list of titles relating to the whole subject may be found in the 

 paper by Pearl, '17. 



