FERTILIZATION REACTION IN ECHINARACHNIUS PARMA. 27 



not highly successful; often none of the methods gave results. 

 The reciprocal is not so difficult. 

 2. Echinarachnius 9 X Arbacia cf. 



The cross Echinarachnius 9 X Arbacia cf as well as the reci- 

 procal cross was made usually during agglutination experiments. 

 Thus, after removing the supernatant sea-water from eggs for 

 agglutination tests these could be used for straight or cross fer- 

 tilization. This method, in addition to being economical, made 

 possible the performing of a large number of experiments during 

 the time the Echinarachnius eggs are at their best. 



1. Allowing the Eggs to Stand. Although as mentioned above, 

 Echinarachnius eggs are not so resistant to sea-water as Arbacia 

 eggs, after three to four hours in sea-water they develop following 

 insemination with Arbacia sperm. Thus on July 4, Echinarach- 

 nius eggs were inseminated with Arbacia sperm at ten-minute 

 intervals up to three hours. The best lot of eggs was that in- 

 seminated after two hours in sea-water and showed five per cent, 

 of development. Addition of Arbacia egg- water to the eggs 

 does not increase the per cent, of those that develop. 



2. Treating the Eggs with Alkali. Treatment with alkali 

 before and after insemination gives a high per cent, of cleavage; 

 the eggs, however, in the later stages, particularly the blastula 

 and gastrula, show marked abnormalities as well as a tendency 

 to disintegrate. 



On July 7, the following experiment was made three times: 



2:40 P.M. Eggs previously procured by straining from ovaries gently cut up 

 in sea-water were divided among seven dishes: 



No. i, uninseminated control in 15 c.c. of sea-water. 



No. 2, eggs +15 c.c. sea-water + i drop /io KOH. 



No. 3, eggs + 15 c.c. sea-water + 2 drops w/io KOH. 



No. 4, eggs +15 c.c. sea -water + 3 drops w/io KOH. 



2:42 P.M. Nos. 2, 3 and 4 inseminated with freshly made thin Arbacia sperm 

 suspension. 



2:45 P.M. Nos. 5, 6 and 7. Eggs in 15 c.c. of sea-water inseminated with 

 same Arbacia sperm. 



2:47 P.M. i, 2 and 3 drops M/IO KOH added to nos. 5, 6, and 7 respectively. 



5:00 P.M. Eggs show five per cent, development; in No. 2, much less in 3, 4, 

 5, 6, 7. Control shows no development. 



With shed eggs the results are strikingly different. 



July 8, 3:10 P.M. To dry eggs from one female, 100 c.c. sea-water added. 

 3 :20 P.M. To each of seven watch glasses a drop of eggs is added. 



