122 



5. It seems not improbable that the length of life and the (-(tming to 

 matui'it.v of the germ cells may be in some way physiologically connected. 



(i. The low ])roductivity (»f the Trnncate skijis a generation when 

 crossed to a liiL>:li-pi-odncii>g strain and reappears in tlie F. generation. !l 

 is ditlicult to correlate the length of life in these sti'ains with the number 

 of offsitriug prtMluced, because it is evident Iroui my other studies that 

 the fertilizing power of the gametes as well as egg prodiution are involved 

 as variable factors in in-oductivity. 



