ACTIVATION OF UNFERTILIZED STARFISH EGGS. 285 



agent itself should have a corrective eflfect similar to that exerted 

 by the agents just named. If the effect of the initial or mem- 

 brane-forming treatment is to cause a partial activation which 

 requires later to be completed by the after-treatment, we should 

 expect it to be a matter of indifference (within certain limits of 

 time) whether the activation is completed in one stage — e. g., by 

 a continuous warming to 32° for 8 minutes — or in several; 

 development ought to follow equally well if the eggs are returned 

 to sea-water after an exposure just sufficient for membrane- 

 formation, and afterward again exposed to the same treatment 

 for an appropriate length of time. Experiment shows that it is 

 in fact possible to substitute for the after-treatment with hyper- 

 tonic sea-water or cyanide a brief exposure either to warm sea- 

 water or to n/260 butyric acid. We have here clear indication 

 that the essential changes produced in the egg by after-treatment 

 with an agent like hypertonic sea-water are not qualitatively 

 different from those caused by the first or membrane-forming 

 treatment, but serve simply to renew and bring to its completion 

 a process which has been initiated by the first treatment but 

 prematurely arrested by the early return to normal sea-water. 

 According to this conception the whole activation-process is 

 unitary in nature and does not consist of two qualitatively 

 distinct and mutually complementary processes, as Loeb has 

 maintained on the basis of his experiments with sea-urchin eggs. 

 The following series (Table XIII.) illustrates the effects of 

 treating eggs, in which membranes have been formed by 3 

 minutes' exposure to 32°, a second time with sea-water at 32° 

 for 4. minutes ; the second exposure was made at varying intervals 

 after the first, ranging from 9 minutes to nearly 4 hours. 



Table XIII. 



After-treatment with Sea- water at 32°. 



June 24. Eggs from several starfish were exposed, about 35 minutes after 

 removal from the animals, to sea-water at 32° for 3 minutes (11.12-11.15 A.M.), 

 and then returned to sea-water. Part of these eggs were left permanently in sea- 

 water for control ; the rest were again exposed to 3 2 ° for 4 minutes, successive portions 

 being thus treated at lo-minute intervals until well after the separation of the second 

 polar body. The condition of the maturing eggs at the time of the second treatment 

 is indicated in the first column. 



