ACTIVATION OF UNFERTILIZED STARFISH EGGS. 29I 



ment with sea-water at 31° and at 34° was also tried; the results 

 were the same except that the after-exposure required at 34° 

 was only a half to a third as long as at 32°, and at 31° about 

 twice as long. The following series at 34° (Table XV.) is 



typical. 



These results show that the effective duration of after-exposure 

 at 34° is about one third of what it is at 32°; at 31° the best 

 results were gained with after-exposures of 8 to 10 minutes. 

 The temperature-coefhcient of the physiological change resulting 

 from the after-warming treatment is thus evidently of the same 

 order as in the case of simple warming without previous mem- 

 brane-formation. This of course is not surprising, since un- 

 doubtedly the same process is concerned in activation by heat 

 whether this is preceded by another treatment or not. 



It is thus plainly a matter of indifference, as regards the effect 



Table XVI. 



Both Membrane-formation and After-treatment by «/26o Butyric Acid 

 September 6. The eggs from one starfish were used; these were few in number, 

 but almost all {ca. 90 per cent.) showed normal maturation, and in the sperm-fer- 

 tilized control almost all formed larvae. The eggs were exposed for one minute to 

 M/260 butyric acid and returned to sea-water; part were left in sea-water as control; 

 the remainder were again placed, 18 minutes later, in «/26o butyric acid, from which 

 portions were returned to normal sea-water at the intervals indicated. These eggs 

 developed as follows: 



Results (Condition of Eggs after 4 Hours and 

 After-treatment. Proportion forming Larvae). 



1. None (control) AH show typical membrane-formation followed by 



irregular change of form and breakdown in nearly 

 all eggs. Only one larva seen. 



2. iV/260 Butyric acid: 2 



m A few eggs are cleaved. Ca. 10-15 per cent, form 



larvae. 



3. Butyric acid: 4 m Cleavages more numerous and more regular than in 



Exp. 2. Ca. 40-50 per cent, of eggs form larvae. 



4. Butyric acid: 6 m Cleavages still more numerous: Most eggs form larvae 



(70-80 per cent.). 



5. Butyric acid: 8 m Like Exp. 4. but fewer eggs form larvae (50-60 per 



cent.). 



6. Butyric acid: 10 m Cleavages are fewer and slower. 25-35 per cent, of 



eggs form larvae. 



7. Butyric acid :12 m Cleavages are still fewer. Ca. 10 per cent, of eggs form 



larvae. 



8. Butyric acid: 15 m Practically none are cleaved. No larvae. 



