LARVAE OF ARBACIA PUNCTULATA 



345 



In the solutions of greater concentration than that of the 

 normal sea-water (Plot 4), there occurred a proportionately 

 greater reduction in size, — an effect which must be looked 

 upon in the light of an inhibiting of growth rather than of a 



Figs. 27 to 31 Experiment 2. Normal sea-water concentrated. 



Fig. 27 2a, figure 28 26 +, figure 29 2c +, figure 30 2d +, figure 31 2e +, 96 

 hrs. Prominent processes on the posterior parts of the body-rods and the ven- 

 tral body-branches. Fusing of the lateral connectives with heavy deposit of 

 calcareous material. Irregularity of structure of skeleton. 



Fig. 32 Experiment 3. Sea-water gradually concentrated by evaporation. 



Fig. 32 M, 96 hrs. Slender rods as in dilute solutions, but processes more 

 prominent; irregularity of form as in concentrated sea water. 



retarding of development, since all reach their maxima at an 

 age of 96 hours. An exception must be made in the case of c + , 

 but its diminution is exceedingly slight and the maximum may 

 lie close to the 96 hour point. The decrease in size in a as 

 indicated by its growth-curve is shared to a less extent by 6 +, 

 and still less by c -f and d -j- ; e + reached its maximum at the 



