Fig. 68. — Development of rolygordius. (After Fraifoxt.) 

 a., Mother sperm cell ; h., c, sperm morulje ; d., spermaluzoa. 

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

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

 mation of stomatodffiura(i^.), and proctodeum (/r.), invaginated to meet archenteron 

 (^.) ; 8. complete gut formed; g. elongation of larva ; ap. s/>.^ apical spot; cii., 

 cihated ring; tteph., primitive nepbridia ; 10. formation of posterior segments; 

 II. rorm of A'iu\t Poly£^ordius. 



