44 HARRIETT M. ALLYN. 



percentage extruded both polar bodies, and both segmented and 

 unsegmented swimmers were produced. The production of a 

 large proportion of the polar bodies and all of the cleavage would 

 appear to be due to the sperm. But that the potassium chloride 

 also had an effect, and opposed to that of the sperm, is seen in 

 the increased percentage of unsegmented swimmers in the KC1 + 

 sperm material above that in the fertilized control. An exposure 

 to potassium chloride of only one minute thus causes suppression 

 of cleavage in KC1 + sperm eggs. 



A delay in sea-water before fertilizing after potassium chloride 

 shows a slight decrease in total number of swimmers, and still 

 further suppression of cleavage, making the percentage of un- 

 segmented swimmers much larger, and showing a very marked 

 decrease in segmented swimmers. 



When the potassium chloride is applied for a longer time before 

 the eggs are removed to ordinary sea-water the decrease in 

 swimmers is much faster, differentiation to swimming forms being 

 interfered with nearly as much as cleavage, showing a stronger 

 potassium chloride action. 



Thus it is seen that the potassium chloride initiates changes 

 which increase with time and which are inimical to normal 

 fertilization. They do not prevent the entrance of the sperm into 

 the egg, but they prevent the normal behavior of the sperm in the 

 egg. Polyspermy is induced, but the suppression of cleavage 

 seems to refer to some other factor also, since in the sections of 

 preserved material no more polyspermy is noted in the case of late 

 fertilization than in early, yet the ill effects of the combina- 

 tion are greater with late fertilization. 



Results are similar for 0.5 c.c. 2 l /2 M KC1 in 50 c.c. of sea- 

 water, but they were complicated by the fact that the female 

 did not seem to be a good one, for the fertilized control cleaved 

 abnormally and many eggs in it did not cleave at all. 



A comparison of the curves made from Table VIII. (Fig. A) 

 brings out these facts graphically. AA represents the increase 

 in swimmers with increased time in KC1 (no sperm). CC repre- 

 sents the decrease in swimmers when the eggs are fertilized at 

 once on removal from potassium chloride, but with increasing time 

 in potassium chloride. BD and B'D break this curve up to repre- 



