LIFE HISTORIES OF ALG^E 
235 
occur within 10 minutes after the gametes have been 
placed together in the water. After the formation of the 
^ I \ 
?%?**& \ k 
FIG. 175. Ascophyllum nodosum (L.) Lejol. A, egg at the time of 
fertilization, surrounded by numerous sperms. X about 200; B, oosperm 
germinating, 6 days old; C, D, somewhat older stages than B. (Redrawn 
from Thuret and Bornet.) 
fertilization-membrane the sperms seem to avoid the 
oOsperm, quite as though they were repelled by some 
substance formed at its surface. 
