354 GRACE MEDES 



Herbst ('06), investigating the effect of increased tempera- 

 ture, found an increase in the number of roots of the multiple 

 arm-rods and in the number with latticed structure. If they 

 were removed from the warmer medium before the time of mesen- 

 chyme formation, the simple rods characteristic of Strongylo- 

 centrotus prevailed. If they were removed at the gastrula stage, 

 multiple-formation was inhibited to a greater degree than when 

 they were transferred at the pluteus stage. 



This leads directly to the consideration of our second ques- 

 tion: ''To what extent may early inhibition be overcome by 

 later favorable conditions?" In Experiment 3, cultures/ and 

 g, we have examples of early treatment with a medium so 

 adverse that, under continuous subjection, life could scarcely 

 be maintained (compare with/ and g, Experiment 2), followed 

 by a later more favorable medium within the range of optimum 

 concentration. At the close of the experiment the larvae 

 approximate so closely the control that they may scarcely be 

 termed subnormal. As far as size is concerned, we have a 

 complete compensation for early inhibition; but the ultimate 

 growth attained is not equal to that which would have occurred 

 had the larvae been subjected during the entire period to a 

 concentration equal to that of these solutions at the close of 

 the experiment, nor so slight as that which would have been 

 produced by continued subjection to solutions of the original 

 concentrations. This tends to confirm Vernon's conclusion 

 that 'Hhe range of the harmful effect of an adverse condition is 

 always greater than the succeeding influence of a favorable one. 

 The larvae never attain the maximum size to which they can 

 develop, nor the minimum at which they can maintain life." 



Our third question, ''In how far may favorable conditions 

 during the first few hours of cleavage so benefit the organism 

 that the later adverse circumstances fail to produce ultimate 

 modification of growth," is more difficult to answer, since, as 

 the data given above show, any sudden change at the time of 

 impregnation has a deleterious effect upon the organism. If 

 the transfer be to a medium intrinsically beneficial, and the 

 subjection be of sufficiently long duration, the injury may be 

 only temporary. 



