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 



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 

 oSsperm, quite as though they were repelled by some 

 substance formed at its surface. 



