ClipArt ETC
"Development of Polygordius. a., Mother sperm cell; b., c., sperm morulae; d., spermatosoa. 1. Ovum with large nucleus; 2. two-cell stage; 3. four-cell stage; 4. blastosphere; 5. gastrula; ac., archenteron; 6. closure of gastrula mouth or blastopore; 7. formation of stomodaeum (st.), and proctodaeum (pr.), which invaginate to meet archenteron (ac.); 8. complete gut formed; 9. elongation of larva; ap. sp., posterior segments; 11. form of adult Polygordius." -Thomson, 1916

Polygordius

"Development of Polygordius. a., Mother sperm cell; b., c., sperm morulae; d., spermatosoa. 1. Ovum…