INITIATION OF DEVELOPMENT IN EGG OF ARBACIA. 



415 



of an equal quantity of uninseminated eggs from the same female 

 in normal sea-water. Unfortunately this was not done. 



(c) July 1 8, 10:00 A.M. 0.5 c.c. of shed eggs (sample of 

 which on insemination gave 98 per cent, membranes) in 10 c.c. of 

 blood Lot A. Following series set up : 



No. i. 5 c.c. of Lot A plus 5 c.c. of sea-water. 



2. 



" 3- 



" 4- 



" 5- 

 " 6. 



ti it 



No. i 



No. 2 " 



" No. 3 " 



" No. 4 " 



" No. 5 " 



7. No. 6 



All inseminated heavily. 



12 : oo M. Cleavages in these eggs as follows : 



Nos. 2, 3, and 4 killed and sectioned. 



The interesting point here is that despite the graded decrease in 

 the quantity of both eggs and blood the inhibitory action of the 

 blood persists. Each lot of eggs was inseminated with the same 

 amount of sperm. This means that the heaviness of insemination 

 steadily increased in the Nos. 2 to 7, for the number of egg's was 

 halved in each successive dilution. It would seem, therefore, that 

 heavy insemination does not necessarily mean an overcoming of 

 the blood block to fertilization. That the failure to cleave was not 

 due to polyspermy we may conclude from the per cent, of cleavage 

 in Nos. 5, 6, and 7, which received relatively to the number of 

 eggs most heavy insemination. However, I should point out that 

 this was the most powerful inhibiting blood encountered in this 

 group of experiments (made during June and to July 20). 



(d*) July 19, 6: 30 P.M. 10 c.c. suspension of shed eggs (sam- 

 ple of 'which gave 98 per cent, membranes) plus 10 c.c. of blood 

 inseminated. 



