ACTIVATION OF UNFERTILIZED STARFISH EGGS. 289 



to 12 minutes. For comparison part of the eggs were after- 

 treated with hypertonic sea-water and cyanide. 



Table XIV. 



M/260 Butyric Acid with After-treatment with Sea-water at 32°. 



August 24. Eggs from one starfish were used. These eggs were not very 

 favorable and a rather small proportion underwent maturation. They were 

 exposed, about 45 minutes after removal, to M/260 butyric acid solution for one 

 minute and then returned to normal sea-water. Twelve to sixteen minutes later 

 they were after-treated as follows, with the results indicated. 



Results (Condition of Eggs 4-5 hours later, and Proportion 

 After-treatment. r at . t- r ■ r n 



of Mature Eggs forming Larvae). 



1. None (control treated 



with butyric acid 



alone) Typical fertilization-membranes in all mature eggs; 



later the eggs assume irregular forms and break 



down. None form larvse. 



2. Hypertonic sea-water 



(250 c.c. s. w. -I-40 

 CO. 2.5 m NaCl) for 

 30 min Markedly favorable effect: most mature eggs are 



cleaved to ca. 32-cell stage. 20-30 per cent, form 



larvee. 



3. M/iooo KCN in sea- 



water for 30 min Eggs cleave as in Experiment 2. Ca. 25-30 per cent. 



form larvae. 



4. Sea- water at 32° for 2 



min After four hours most eggs are irregular and un- 



cleaved; a few are cleaved. Very few form larvae 

 ( < I per cent.). 



5. 32° for 3 min Like Exp. 4, but more eggs are cleaved. Few larvae, 



— I per cent, or less. 



6. 32° for 4 min Cleavages are more numerous than in Exps. 4 and 5. 



Ca. 5 per cent, of mature eggs form larvae. 



7. 32° for 5 min Ca. 20-30 per cent, are cleaved. Ca 5 per cent, form 



larvae. 



8. 32° for 6 min Cleavages are more numerous than in Exp. 7. Ca. 



40-50 per cent, larvae. 



9. 32° for 7 min Most eggs in 16- to 64-cell stages. 50-60 per cent. 



form larvae. 



10. 32° for 8 min Like Exp. 9, but somewhat less favorable. Ca. 50 



per cent, form larvae. 



11. 32° for 10 min After five hours few eggs are cleaved and cleavages are 



less advanced than in Exps. 9 and 10. Ca. 10-15 

 per cent, form larvae. 



12. 32° for 12 min Almost none have cleaved after five hours. Practic- 



ally none form larvae (one blastula seen). 



