FERTILIZATION-REACTION IN ECHINARACHNIUS PARMA. 283 



temperature, the physiological condition of the egg when shed 

 as determined by its size and presence of the jelly hull the time 

 in the breeding season, and the bulk of the eggs (that is, their 

 concentration in a given volume of sea-water). To make com- 

 parisons, therefore, Goldfarb took precautions especially with 

 reference to the last-mentioned factor, using as near as possible 

 the same concentration of egg suspension. Nothing is clearer 

 from these observations of his than the fact that eggs which are 

 normally fertilized in sea-water after coming into sea-water and 

 failing of insemination gradually die ; for the cytolyzing egg is a 

 moribund egg. Since it was not my intention to investigate the 

 effect of various factors on this sea-water cytolysis and Gold- 

 farb's work made such an investigation unnecessary I gave no 

 particular attention to them in my observations. All that I wished 

 to do in my study was to compare the rate of cytolysis in sea- 

 water of eggs previously unexposed to butyric acid with those 

 eggs in sea-water previously exposed for varying lengths of 

 time to the action of this acid. My observations brought out a 

 highly interesting fact ; namely, . that eggs under-exposed to 

 butyric acid (i.e., eggs that formed no membranes after trans- 

 ferral to normal sea-water) cytolyze at a slower rate than unex- 

 posed eggs. In other words, underexposure to butyric acid is 

 beneficial to eggs in delaying the normal cytolytic effect of sea- 

 water. To be sure, the factors temperature, seasonal variation, 

 physiological condition of the ova, etc., play a part in the process ; 

 but, obviously, in any given observation in which a comparison is 

 made between sea-water cytolysis and butyric acid cytolysis, 

 since the eggs were from the same female and were approxi- 

 mately of equal mass in equal volume of water in the various 

 dishes, the conditions were uniform. 



Briefly, I found that if eggs of the sand dollar, Echinarachnius 

 parma, after exposure to a mixture of n/io butyric acid and sea- 

 water (in the proportions 2 c.c. of acid plus 50 c.c. of sea-water) 

 be transferred at varying intervals up to two or three minutes to 

 dishes of pure clean sea-water they are cytolyzed during the 

 ensuing thirty-six to forty-eight hours to complete disintegration. 

 The rate of cytolysis such factors as temperature, physiological 

 condition of the eggs, seasonal variation, and mass of eggs to 



