398 GRACE MEDES 



sideration was omitted and noted the resulting abnormalities. 

 Whatever processes were modified or inhibited he assumed to be 

 directly affected by the lack of that substance. 



Sodium and hydroxyl he looked upon as general conditions of 

 development, since their omission from the medium resulted 

 in complete inhibition of all the life processes. By general 

 condition he does not mean that the substance is necessarily 

 indispensible for every separate process, biit for some one or 

 more fundamental process operating at each period of develop- 

 ment. He contrasts the role of calcium to that of sodium in 

 its effect on the cohesion of the cells and ascribes the injurious 

 action of the Ca-free medium to the "Auflockerung des Zellen- 

 verbandes/' which he assumes to be caused directly by the so- 

 dium. It may be that this lack of cohesion of the cells is con- 

 cerned with the increased size of the larvae in the NaCl solutions. 



Herbst assigns an important role to the carbonates in skele- 

 ton-formation, since in the alkaline C02-free medium only 

 small, rudimentary tri-radiate spicules are laid down. Later 

 on, however, the same larvae may begin to form arms and become 

 fairly normal. He suggests that the secondary regulation may 



Figs. 103 and 104 Experiment 16. NaCl, 0.60 :\I. 



Fig. 103 16^, 72 hrs. Greatly reduced in size, but proportions maintained 

 about as in the normal. Many perforations in the posterior fused portion of the 

 body-rods. Anal arms unfused except for one cross-branch. Processes all 

 very long and prominent. Oral arms elongated. 



Fig. 104 IQh, 72 hrs. Still further reduction in size, about 1/5 the size of 

 the control. All the typical modifications for NaCl solutions accentuated. 



Figs. 105 and 106 Experiment 19. Sea-water + NaCl. 



Fig. 105 19a, 48 hrs. Control. 



Fig. 106 196, figure 107 19c, 48 hrs.; figure 108 196, figure 109 19c, figure 110 

 19d, 72 hrs.; figure 111 196, figure 112 19c, figure 113 19c^, 96 hrs.; figure 114 196 

 figure 115 19c, figure 116 19d. 120 hrs. In the stronger solutions increasingly 

 great reduction in size, and early fusion of the body-rods,- followed by develop- 



