_РгАтЕ IV. 
Living Eggs of Cynthia partita; Fourth Cleavage to Gastrula. 
ig. 37.—Sixteen-cell stage viewed from vegetal pole. 
ig. 38.—Sixteen-cell stage, from the animal pole, yellow protoplasm around the nuclei. 
ig. 39.—Twenty-two cell stage, from the vegetal pole; four mesoderm cells (yellow), ten endoderm, 
chorda and neural plate cells (gray) and eight ectoderm cells (clear). 
. 40.—Same stage viewed from the posterior pole. 
. 41.— Egg passing into the 32-cell stage; postero-dorsal (vegetal pole) view. 
ig. 42.— Thirty-two-cell stage, postero-dorsal view. 
ig. 43.— Forty-four-cell stage; posterior view, showing separation of ars pon (m'eh) from muscle 
cells (ms.). 
. 44.—Same stage, dorsal view, showing subdivision of endoderm cells. 
ig. 45.—Similar stage, posterior view, showing separation of another mesenchyme cell from a muscle 
cell. 
ig. 46.—Seventy-four-cell stage, dorsal view, showing division of 4 chorda and 4 neural plate cells ; 
there are 10 mesenchyme and 6 muscle cells, besides 10 endoderm cells. 
ig. 47.—One dena and sixteen. cell-stage, showing the Begining of gastrulation, also the neural 
te, chorda, muscle and mesenchyme cells. 
ig. 48.— Slightly older stage showing advaneing gastrulation with inrolling of cells at edge of blastopore. 
