BEHAVIOR OF THE GAMETES 225 



the egg, when present in dilute solution, caused the sperm of the sea urchin to 

 loose their motility and to become clumped together or agglutinated. A little 

 later, F. R. Lillie, '13, '14, '15, studied the activity of the egg water of the 

 sea urchin, Arbacia, extensively. Lillie associated the egg secretion found in 

 the egg water with a definite theory concerning the mechanism of fertilization. 

 He called the substance given off when the sea-urchin egg is allowed to stand 

 in sea water, "fertilizin"; for, according to his results, washed eggs deprived 

 of this egg secretion fail to fertilize. Only ripe eggs give of! fertilizin according 

 to his observations. Lillie found further that the activities of the sperm, intro- 

 duced by means of a pipette into the egg-water solution are changed greatly. 

 At first they are activated, to be followed by an agglutination. Moreover, a 

 drop of egg water introduced into a sperm suspension activates the sperm 

 and appears to influence them chemically, causing them to be attracted to 

 the drop. Lillie therefore concluded that fertilizin has a threefold action upon 

 the sperm: 



(1) that it activates the sperm (that is, stimulates their movement), 



(2) attracts the sperm by a positive chemotaxis, and 



(3) agglutinates the sperm, that is, causes the sperm to associate in clumps. 



The agglutination effect F. R. Lillie found is reversible in most sea-urchin 

 sperm, providing the egg water containing fertilizin is not allowed to act too 

 long. On the other hand, in the annelid, Nereis, agglutination of the sperm is 

 "essentially permanent" (Lillie, F. R., '13). Lillie placed most emphasis upon 

 the "agglutinin" factor in the egg water. He further postulated that fertilizin 

 not only affected the sperm, but also activates the egg to cause its development 

 (see theory at end of chapter). Lillie also obtained another substance from 

 crushed or laked eggs which combines "with the agglutinating group of fer- 

 tilizin, but which is separate from it as long as the egg is inactive." This 

 substance present within the egg he called "antifertilizin." 



Since the time of F. R. Lillie's original contribution, the subject of fertilizin 

 and antifertilizin has been actively investigated by various students of the 

 problem. Some investigators criticized the conclusions drawn by Lillie, but 

 more recent work substantiates them. For example, M. Hartmann, et al. ('40), 

 working on the sea urchin, Arbacia pustulosa, and Tyler and Fox ('40) and 

 Tyler ('41 ), using eggs from Strongylocentrotus purpuratus, find that fertilizin 



Fig. 116 — {Continued} 

 polar bodies (P.B.); fusion of chromosomal vesicles to form egg pronucleus (E.N.). 

 (M) Movement of sperm nucleus, aster, and of surrounding yellow-pigmented and clear 

 protoplasm to the posterior pole of the egg. The copulation path of egg pronucleus 

 (E.N.) to meet the sperm nucleus is in progress. (N) Sperm aster has divided; egg 

 pronucleus progresses along its copulation path toward posterior pole of egg to meet the 

 male pronucleus. (O) Egg and sperm pronuclei are making contact with each other. 

 (P) Pronuclei associate and begin to form early prophase conditions of the first cleavage. 

 (Q) Metaphase of first cleavage. (R) Anaphase of first cleavage. (S) Late anaphase 

 of first cleavage. 



