Scientific Proceedings. 



(i33) 69 



with sperm. A certain percentage of these eggs rose to the sur- 

 face of the water in the usual way, while the eggs which had not 

 formed a membrane either did not develop at all, or developed in 

 the somewhat abnormal and slow way characteristic of the treat- 

 ment by hypertonic sea water alone. 



The reader will notice that the eggs were submitted first for 

 about two hours to the hypertonic sea water and then exposed to 

 the acid. When the order was reversed, and the eggs were exposed 

 to the acid first and afterward to the hypertonic sea water for about 

 two hours, most of them died without developing. This seemed 

 rather strange, in view of the fact that in the case of sperm fertiliza- 

 tion, the membrane formation is the first act in the series of events, 

 while in the above-mentioned experiments it was the last. It oc- 

 curred to the author that by shortening the time of exposure of the 

 egg to the hypertonic sea water, he might also accomplish the last 

 postulate of a complete imitation of the process of fertilization by 

 physico-chemical means, namely, to get the order of events identical 

 in both cases. This idea proved correct. It was found that when 

 the unfertilized eggs were exposed for about one to two minutes to 

 50 c.c. of sea water, to which about 3 c.c. 71/10 acetic acid were 

 added, the majority of the eggs formed the membrane characteris- 

 tic of the entrance of the spermatozoon. If these eggs were after- 

 ward exposed for from 30 to 40 minutes to 100 c.c. of sea water, 

 to which 14 c.c. or 15 c.c. of a 2 y 2 n solution of NaCl were added, 

 those of the eggs which had formed membranes developed into 

 swimming larvas that rose to the surface. The author has raised 

 these larvas and they develop into perfect plutei as fast as the 

 larvas of eggs fertilized with sperm. 



It is very remarkable that when the order is reversed and the 

 eggs are put first into the hypertonic sea water for about 40 minutes, 

 and then into the acidulated sea water for about one or two min- 

 utes, not a single larva is formed, and the eggs behave on the 

 whole as if they had been exposed to the acid alone. If it is 

 desired to put the eggs into the hypertonic sea water first and then 

 expose them to the acid, it is necessary to expose them to the 

 hypertonic sea water at least an hour and a half in order to obtain 

 larvas. On the other hand, if the eggs are treated with acid first 

 and then exposed to the hypertonic sea water for from an hour and 



