Smith. — Gastrulation in Aurelia. 



PLATE 11. 



ABBREVIATIONS. 



bl'po. Blastopore. 



cav. sg. Segmentation cavity. 



cl. Immigrated cell. 



cedent. Ccelenteron. 



cog. Coagulum. 



ec'drm. Ectoderm. 



en'drm. Entoderm. 



nl. Chromatic portion of degenerated nucleus. 



nl. ec'drm. Nuclei of deeper portion of ectoderm. 



Figures 7, 9, and 10 are from different sections of the same individual. 

 Fig. 7. Section through the blastoporic canal and nearly perpendicular to it. 

 X410. 



8. Section at a stage preceding invagination. It shows an immigrated cell 

 in which the nucleus has degenerated. X 385. 



9. Section before the close of gastrulation, showing an immigrated cell in 

 the segmentation cavity. X 410. 



10. Section from the same individual as Figure 9. It contains an immigrated 

 cell in the coelenteric cavity. X 410. 



11. Section of agastrula with two immigrated cells contained in the coelen- 

 teric cavity. X 385. 



12. Section from the same individual as Figure 3, to show the appearance 

 when the gastrula is cut parallel to, but at one side of, the blastoporic 

 canal. X 385. 



