FERTILIZATION IN PLATYNEREIS MEGALOPS. IO3 



KOH. — Eggs were teased out of the female directly into sea- 

 water plus KOH in various proportions. Or, eggs from dried 

 females were placed in the solution. After remaining from thirty 

 seconds to two minutes in the alkaline sea-water the eggs were 

 inseminated dry and flooded with sea-water. In other cases in- 

 seminations were made in the solutions. Washed eggs were 

 similarly treated. Whatever the method alkaline sea- water 

 never gave cleavage. (Cf. sections on cross fertilization and 

 artificial parthenogenesis.) 



Hypertonic and Hypotonic Sea-water. — Eggs, both washed and 

 dry, were treated with 2j^ M KCl + sea-water as follows: 



I. I drop 2I M KCl -1- 19 drops of sea-water. 



Dry sperm were added at once and the dishes flooded with 

 sea- water after five minutes. Or, after treatment for varying 

 number of minutes the eggs were inseminated dry. The eggs 

 developed no farther than with KCl treatment alone (see 

 beyond) ; they form jelly and maturate. 



Hypotonic solutions used similarly gave no cleavage. 



Ether. — ^The following table is a summary of the experiments 

 with ether: 



"Teased" eggs are those got by cutting up the female in the 

 ether-sea-water. 



A few eggs form jelly and maturate after the ether treatment. 

 Compared with sea-water inseminations, ether cuts down the 

 per cent, of maturations. According to R. S. Lillie ('12) star- 

 fish eggs resistant to fertilization may be rendered normal by 

 ether in low concentration. In Platynereis the condition is 

 different. The egg is not rendered resistant to fertilization by 

 the action of sea-water; it is weakened through loss of something 



