12 Microscope Slides:

1(d). Sea urchin, unfertilized eggs
2(d). Sea urchin, fertilized eggs
3(d). Sea urchin, two cells
4(d). Sea urchin, four cells
5(d). Sea urchin, eight cells
6(d). Sea urchin, sixteen cells
7(d). Sea urchin, thirty-two cells
8(d). Sea urchin, morula
9(d). Sea urchin, blastula
10(d). Sea urchin, blastula, beginning gastrulation
11(d). Sea urchin, blastula, progressive gastrulation
12(d). Sea urchin, pluteus larva.