28 E. E. JUST. 



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



No. 2, Eggs+ 15 c.c. of sea-water + i drop n/io KOH. 



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



No. 4, Eggs+ 15 c.c. of sea-water + 3 drops M/IO KOH. 



3:22, Nos. 2-4 inseminated each with one drop of freshly prepared active Arbacia 

 sperm suspension. 



3 124. Nos. 5, 6, and 7, each with 15 c.c. of sea-water inseminated with one drop 

 of same Arbacia sperm. 



3:26. To nos. 5, 6 and 7 respectively are added i, 2 and 3 drops of M/IO KOH. 



5:00. These eggs show high per cent, cleavage (90 per cent, in no. 4), but also 

 a tendency to lose their membranes when put in normal sea-water. Control, no 

 development. 



3. Insemination with Excess of Sperm. The method of heavy 

 insemination succeeds with Echinarachnius eggs, giving ten to 

 twenty-five per cent, of cleavage. The later stages are far 

 superior to those eggs in which crossing has been induced through 

 alkali treatment. 



July 3, 9:10 A.M. Eggs removed from ovaries divided into three lots A, B 

 and C. Lot A inseminated at 9:15 A.M. with heavy Arbacia sperm; Lot B similarly 

 at 11:00 A.M.; and Lot C similarly at 2:55 P.M. Lot A shows 13 per cent, of de- 

 velopment at 2:50. Lot B 8 per cent. Lot C at 5:00 P.M. shows no development. 



July it, 9:30 A.M. 1/2 c.c. of dry Echinarachnius eggs placed in 10 c.c. of 

 sea-water. 10:05 A.M., five drops of eggs in each of four watch glasses (Series I.) 

 containing i, 2, 3 and 4 drops of freshly prepared Arbacia suspension. To each of 

 four watch glasses (Series II.) containing five drops of eggs, I, 2, 3 and 4 drops of 

 Arbacia sperm added. Watch glass no. 9 uninseminated control; no. 10, insemi- 

 nated with Echinarachnius sperm. 



1:30 P.M. Uninseminated control, no development. Eggs inseminated with 

 Echinarachnius sperm 98 per cent, developing. Eggs of both series inseminated 

 with Arbacia sperm developing 25 per cent, in most dishes. 



These experiments with heavy insemination show that the 

 eggs develop best when inseminated soon after procured; also, 

 that dry eggs are better than "ovary eggs." Whether eggs are 

 added to sperm or vice versa is of no monent, but sperm must be 

 fresh. The eggs treated with dense sperm suspension develop 

 more nearly like the straight fertilized eggs than either the alkali 

 treated or the stale eggs. The larvae are vigorous and active, 

 swimming to the top as do normal larvae. 1 



The cross Echinarachnius 9 X Arbacia cf succeeds far better 

 than the Arbacia 9 X Echinarachnius cf. 2 Indeed in some 

 cases the Arbacia egg is in no wise affected by Echinarachnius 



1 Larva? from this cross were kept for four weeks. 



2 Cf. Gemmil's results with the cross, Cribrella X Asterias. 



