LARVAE OF ARBACIA PUNCTULATA 



363 



rods in the arms. Figure 43, Yd, is a typical specimen. Four 

 unfused rods are present on each side, arising at intervals along 

 the transverse rods and the ends of the latter have bent ante- 

 riorly and elongated into additional ones. In figure 47, Yd, 96 

 hours, four rods are present in each anal arm, and the promi- 

 nent openings in the lattice-work indicate incomplete fusion. 



TABLE 7 

 Constants, Experiment 6. Solution a (Control) 



Although all the typical parts of the skeleton are present, the 

 specimen is marked by a slight lack of symmetry. In many 

 individuals, this irregularity is much more evident, especially in 

 regard to the cross-bars in the anal arms (fig. 48 be, 96 hours). 

 Here even the oral arms have shared in multiple rod-formation 

 and, at the point of fusion of the transverse rods, an additional 

 rod is formed. 



