LARVAE OF ARBACIA PUNCTULATA 



373 



all the rest the specimens were smaller throughout the entire 

 1 died. 



In Experiment 10 still greater percentages of NaHCOs were 

 employed in order to obtain the hmit of endurance at early 

 stages. In Experiment 9 an inhibition of growth was plainly 

 discernible in the stronger solutions, even dm-ing the early 

 periods, but judging from the active movements of the specimens 

 during the first 48 hours, it was evident that much stronger 

 solutions^could be employed. 



Plot 11 



Experiment 10. July 15, 1915 



a Sea-water 



h 90 cc. S. W. + 10 cc. 0.45M NaHCOg 



c 80 cc. S. W. + 20 cc. 0.45M NaHCOs 



d 70 cc. S. W. + 30 cc. 0.45M NaHCOs 



e 70 cc. S. W. + 40 cc. O.^^M NaHCOs 



f .50 cc. S. W. + 50 cc. 0.45M NaHCOs 



Figures 75 to 80 show specimens from the various solutions 

 at the age of 24 hours. In a (fig. 75) the three branches of the 

 tri-radiate spicule have elongated into body-rod, transverse 

 rod and dorso-ventral connective, and the rods of the anal 

 arms are beginning to form. In h (fig. 76) gastrulation has 

 just taken place, producing individuals which appear abnormal 

 only in lack of skeletons. This culture, however, contained on 



THE JOURNAL OF MORPHOLOGY, VOL. 30, NO. 1 



