INTRODUCTORY 



;v-:^/>.'5-- \ ; i-> : - T '; : * -'.-V^.V . "'-.: ' - " 



; 



' : -, ^-U ..; &g 



' .'. *> .' -*i ' -' /--*."- C... *--..> ,*,*, 



FIG. 3. 



^4, Large spherical egg (female gamete) of Bladder Wrack (Fucus), surrounded 

 by many small motile spermatozoids (male gametes). (After Thuret. x 330.) 



B, Human gametes highly magnified : egg to the right, spermatozoon to the 

 left. The egg is enclosed in a transparent envelope which disappears during 

 development. Each division of the scale represents .05 mm., or about 7-, 1 ,,, inch. 



