1(14 DEVELOPMENT. 



196. Spermatozoa. Examine the demonstration of living .spermatozoa of the 

 sea-urchin. 



197. Unfertilized Eggs. Draw examples of the living unfertilized eggs of the sea- 

 urchin. 



198. Fertilization. Examine the sea-urchin eggs to which a suspension of sper- 

 matozoa has been added. Notice the spermatozoa crowding round the eggs and the 

 formation of a membrane around the fertilized eggs. 



