LARVAE OF ARBACIA PUNCTULATA 



379 



(lie) and in figure 86 (9/) are of approximately the same 

 size and both are 48 hours old. In figure 91, the arms are 

 somewhat heavier, but the individual rods comprising them 

 have not fused so greatly and the spines, though reduced in 



Figs. 88 and 89. Experiment 11. NaoCOa. 



Fig. 88 11a, 48 hrs. Control. 



Fig. 89 lie, 48 hrs. All the structures slightly heavier, but in a less ad- 

 vanced stage of fusion than the control, indicating influence of increased Na- 

 content. 



Fig. 90 lid, 48 hrs. Same as above, but influence of Na less pronounced. 

 Resembles more closely those in the NaHCOa solutions. Symmetry. 



Figs. 91 and 92 lie, figures 93 and 94 11/, figure 95 Ug, 48 hrs. Increas- 

 ing inhibition of growth. Gradual loss of evidence of Na influence and ac- 

 quirement of CO3 characters; such as, heavy symmetrical skeletons, with highly 

 fused arm -rods. 



number, are still present. In other specimens of the same solu- 

 tion (fig. 92) spines are lacking. Figures 93 and 94 represent 

 two of the extreme variants of solution /. In 92, spines have 

 disappeared, but the rods have not fused to a greater extent 

 than in the control culture (fig. 88). Figures 96 and 97 are 



