It 



FIG. 68. Development of Polygordius. (After FRAIPONT.) 



#., Mother sperm cell ; 3., c., sperm morulae ; d., spermatozoa. 



i. Ovum with large nucleus ; 2. 2-cell stage ; 3. 4-cell stage ; 4. blastosphere ; 

 5. gastrula ; ac., archenteron ; 6. closure of gastrula mouth or blastopore ; 7. for- 

 mation of stomatodaeum^z 1 .), and proctodaeum (/r.), invaginated to meet archenteron 

 (#.) j 8. complete gut formed; 9. elongation of larva; ap. sfi., apical spot; "/., 

 ciliated ring; neph., primitive nephridia ; 10. formation of posterior segments; 

 ii. Form of adult Polygordius. 



