STUDIES OF FERTILIZATION 561 



up in the vial, fertilized and allowed to settle, the supernatant 

 fluid is very powerfully agglutinative. The experiment was 

 repeated a sufficient number of times to make certain of this 

 result. 



A number of tests were also made with the object of determining 

 if the eggs of Nereis continued to produce agglutinin after fertiU- 

 zation. These showed that the eggs cease very quickly their 

 production of agglutinating substance. None could be detected 

 during the maturation period, but apparently there is a second 

 production about the time of the first cleavage. On this point I 

 v/ish to be understood to speak with reserve. The swelling of 

 the jelly secreted at fertihzation makes the eggs very bulky, and 

 the jelly itself takes up any egg secretion, so that there are consid- 

 erable technical difficulties in making satisfactorj^ tests. 



The fact that stands out perfectly plainly in the case of Nereis 

 is the sudden increase in secretion of agglutinin into the sea- 

 water just after insemination, followed by cessation of its pro- 

 duction. The spermatozoa give absoluteh^ positive tests. As 

 will be shown later, the observations on the normal fertihzation 

 are in complete harmony with this. 



The difference between Nereis and Arbacia in these respects 

 is thus sharply marked. However, it should be remembered that 

 the unfertilized eggs of Arbacia have formed both polar bodies, 

 whereas those cf Nereis are in the stage of the germinal vesicle. 

 It may be that eggs of Arbacia in the germinal vesicle stage are 

 relatively impermeable in the same sense as those of Nereis. 



9. HETERO-AGGLUTINATION AND THE QUESTION OF SPECIFICITY: 

 REACTIONS BETWEEN NEREIS AND ARBACIA 



The demonstration of intraspecific sperm-agglutinating sub- 

 stances derived only from the ova having been made, the question 

 arose whether these substances were essentially the same in both 

 species, or different. If the same, the egg-extract of each should 

 agglutinate the sperm of the other. A number of tests were 

 therefore made which demonstrated conclusively that the sub- 

 stances are decidedly different with reference to their cross-agglu- 



