542 FRANK R. LILLIE 



water to 2 parts ovaries and eggs of Arbacia; the fluid was filtered 

 off. Undiluted it had a powerful effect on Nereis sperm but 

 was negative at 1/16 dilution; 1 cc. was then placed in each of 

 three tubes A, B, C. To A was added 2 drops of an aggregative 

 Nereis sperm-suspension, to 5 4 drops of the same, to C 8 drops 

 of the same. Precipitates formed in all. On testing the super- 

 natant fluids all were found to be negative to Nereis sperm. 

 The hetero-agglutinating substance was completely fixed even 

 in A. Tested for the iso-agglutinating substance, A was shown 

 to be equal in power to the control. The tests gave: 



(A) 1/800 — faintest reaction 

 Control 1/800 — faintest reaction 

 (A) 1/400 — 12 second reaction 

 Control — 1/400 — 8 second reaction 



Thus while all the Nereis-active substance was destroyed the 

 iso-active substance remained in full amount. 



This is of course conclusive; but I was also able to show that 

 the sperm of Ctenolabrus (teleost) may precipitate the hetero- 

 active substance leaving the iso-agglutinating substance intact. 

 The hetero-active substance would therefore appear to be rather 

 generally toxic to foreign sperm. It is present in greater quantity 

 in the blood than in egg solutions as shown by definite experi- 

 ments which need not be quoted in detail. It is rather probable, 

 indeed, that its presence in the egg solutions is due to contami- 

 nation by the blood. But I did not test this out fully, though it 

 could readily be done by successive washings of the eggs. 



A rather embarrassing fact that appeared in the course of the 

 above tests is that Nereis sperm may destroy considerable quanti- 

 ties of the iso-agglutinating substance if present in excess of the 

 amount required to fix the hetero-active substance. This came 

 out first in the test of C (under June 19 above), which contained at 

 least 4 times the amount of Nereis sperm needed to fix the hetero- 

 active substance, for the supernatant fluid in this tube turned out 

 to be several times less active in its iso-agglutinating properties 

 than the untreated control. It looked as though the Nereis 

 sperm would combine more actively with the iso-agglutinating 

 substance than the Arbacia sperm itself. 



