LARVAE OF ARBACIA PUNCTULATA 



377 



tendency toward variations in this respect as is shown in the 

 control. 



In the specimen illustrated by figure 87, the main part of the 

 additional calcareous deposit occurred on the dorso-ventral con- 

 nectives which were turned laterally instead of dorsally. The 

 oral arms may be said to be directed posteriorly, or to be lack- 

 ing entirely, and the dorsal body-branches to be very highly 

 developed. A few individuals of this type were found, not only 

 in this experiment in the stronger solutions, but also in similar 

 cultures with individuals from different parents. 



Experiment 11 deals with the effects of NaoCOs, which was 

 employed because upon hydrolysis it gives hydroxyl ion concen- 

 tration greater than that given by NaHCOs. The following 

 solutions were used: 



Experiment 11. Plot 12. July 9, 1915 



a Sea-water 



h 99.8 cc. S. W. +0.2 cc. 0.45M NajCOs 



c 99.6 cc. S. W. + 0.4 cc. 0.45M NazCO, 



d 99.4 cc. S. W. + 0.6 cc. 0.45M NajCOs 



e 99.2 cc. S. W. + 0.8 cc. 0.45M NajCOs 



/ 99.0 cc. S. W. + 1.0 cc. 0.45M NaaCO, 



g 98.8 cc. S. W. + 1.2 cc. 0.45M NazCOs 



The following measurements were obtained: 



24 HOURS 



24.40 

 27.82 

 36.72 

 32.14 

 20.30 

 5.63 



36 HOURS 



55.72 

 60.55 

 62.68 

 56.13 

 38.32 

 15.69 

 0.06 



68.16 

 71.94 

 72.13 

 64.17 

 45.12 

 21.34 

 2.85 



72 HOURS 



84.31 

 85.97 

 83.89 

 74.76 

 54.73 

 28.14 



96 HOURS 



92.26 

 91.90 

 88.03 



77.08 

 55.91 



120 HOURS 



96.48 

 94.37 

 89.78 

 78.01 

 56.22 



The specimens of the control culture of this experiment 

 greatly exceed in size those of the general average for the corre- 

 sponding season. Here again, the effect of the increased alka- 

 linity is shown in the growth-curves produced by the various 

 solutions. The specimens in h, c and d are in advance of those 

 in a at the ages of 24 and 36 hours, but b drops behind after 



