SUSCEPTIBILITY IN EGGS OF AMPHITRITE. 



39 



So 



60 



40 



20 



I have taken the above experiments as typical examples. I 

 have occasionally obtained a much larger per cent, of swimming 

 eggs, frequently a smaller number, and sometimes none. Accept- 

 ing the number of swimming structures as a fair test of develop- 

 ment of this kind, we may make again the following statements : 



I. In the differentiation of unfertilized eggs of Amfhitrite, pro- 

 duced by transference, squirting or other methods of agitation, 

 there are at least two periods in which they are highly suscep- 

 tible, one thirty to forty-five minutes, the other eighty to one 

 hundred minutes after being put into sea-water. 



I have attempted to depict this idea on ordinate paper, shown 

 in the accompanying figures. Abscissas represent time from 

 the beginning of an experiment, ordinates the relative number of 



20 40 60 80 100 120 140 



FIG. I. i. Gently transferred, experiment I. 2. Very moderately squirted, 

 experiment 26. 3. Moderately squirted, experiment 2. 4. Violently squirted, 

 experiment 4. 



swimming eggs in 2,000 of each lot. Fig. i gives the results of 

 four experiments produced by different degrees of agitation. 

 Fig. 2 shows all the observations of these four experiments com- 

 bined in a single line ; where two observations were made at the 

 same time their average is taken (in one case only). The dotted 

 line gives my idea of the curve of susceptibility, as brought 

 about by a moderate degree of shaking. 



2. By comparing experiments i, 2 and 3 (Figs, i, i, 2, 3) we 

 find slight agitation is more effective in the second period than in 

 the first ; rougher treatment causes more to develop in the first 

 period, but injures some in the second. 



1 60 



