328 MYRA MELISSA SAMPSON. 



results in abnormal development. It may occur if mature ova 

 are inseminated in sperm filtrates. To determine this, two 

 milliliters of washed Arbacia eggs were placed in twenty-five 

 milliliters of sperm filtrate and, as a control, a similar quantity 

 in twenty-five milliliters of sea-water. These were inseminated 

 immediately, or after exposure to the filtrate or sea-water for 

 from one minute to four hours. Frequent observations were 

 made to determine whether the filtrates affect either fertilization 

 or development. The effects observed are as follows in the ova 

 fertilized in the filtrate and allowed to develop in it: lack of a 

 normal fertilization membrane; abnormal changes in shape; a 

 low percentage of dividing ova ; abnormal division ; delayed and 

 abnormal development; and cytolysis. In the controls normal 

 fertilization and development occurred. Similar results were 

 obtained in thirteen series of experiments in which several filtrates 

 were used. Gemmil (1900) describes similar conditions resulting 

 from heavy insemination and finds them accompanying poly- 

 spermy as demonstrated by histological examination. 



The abnormal development which occurs when ova are in- 

 seminated in the sperm filtrates may be a result of an abnormal 

 fertilization reaction. If this is due to changes in the ova in 

 the filtrate, it may be that such changes are reversible if the 

 exposure to the filtrate is of short duration. Ova of Arbacia 

 punctulata were exposed to filtrates made from two per cent, 

 suspensions for from one minute to two and a half hours, and to 

 filtrates from five per cent, suspensions for one to thirty minutes. 

 Some were inseminated in the filtrates and others after transfer to 

 sea-water. Few of those inseminated in the filtrate developed 

 normally. The majority of those inseminated after transfer 

 to sea-water formed fertilization membranes and developed 

 normally. The changes produced in the ova by the filtrates, 

 which tend to prevent normal reactions between ova and sperm, 

 are reversible if the period of exposure is brief. Prolonged 

 exposure to filtrates, however, wrought such changes in the 

 majority of ova that they lost their capacity for fertilization and 

 development completely. 



Ova of Strongylocentrotus purpuratus exposed for short periods 

 to sperm filtrates may not exhibit any change in optical appear- 



