Formation of Ganglions and Stomodaeum in Normal and Separate Embryos of Horseshoe Crab, Tachypleus tridentatus

概要

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The process of formation of ganglions and stomodaeum was examined in normal embryos and separate embryos whose stomodaea did not pass through the middle of the nervous system. The following facts were established. 1) The structure of the stomodaeum is recognizable aftre stage 14. 2) The cell masses of ganglions are observed clearly after stage 16; the commissures are stained by eosin after stage 19. 3) The final number of ganglions is settled by stage 19; this means that the formation of segment primordia is settled by stage 19. 4) The stomodaeum passes through the area between the commissure of the first prosomatic ganglions (chelicera segment) and that of the second ganglions. 5) The crossing of the stomodaeum and the nervous system is thought to be formed at stage 18-19. 6) The crossing is constructed during the clustering of the cells composing the brain; the stomodaeum does not determine the pathway for the clustering of these cells. 7) The position of the mouth is not appropriate as an indicator for determination of homologous segments among arthropodan species. 8) The crossing does not constitute a valid reason for rejecting the idea that Deuterostomia have originated from Protostomia.
社団法人日本動物学会の論文
1990-04-15