328 



DEVELOPMENT OF ASCIDIANS 



Fig. 4. Phalliisia tadpoles, a, development in O.IM sodium malonate; 

 h, development in 6 X 10~2 2Vf malonate. 



sented some larvae which developed after the treatment. They 

 have almost normal "heads," but the tails are very abnormal — 

 atrophic, distorted, and poorly functional, with the chordal cells 

 partially fused and randomly disposed, apparently as a conse- 

 quence of the disturbed differentiation of the muscle-cells. The 

 above results were obtained also when the treatment was inter- 

 rupted at neurula stage. 



Treatment with Selenite. Eggs at the 2-cell stage reared in 

 selenite solutions at 1 X 10~^ to 4 X 10"^ M can develop into 

 larvae (Fig. 5a). The larvae from a 1 X 10~^ M solution cannot, 

 however, get out of the membranes, their tails are poorly devel- 



Fig. 5. Phallusia tadpoles, a, development in 1 X 10-^ M sodium sele- 

 nite; b, development in 6 X lO^^ M selenite, until the neurula stage. 



