LIFE HISTORIES OE ALG^E 



235 



occur within lo minutes after the gametes have been 

 placed together in the water. After the formation of the 



Fig. 175. — Ascophyllum nodosum (L.) Lejol. Ay 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. 



