Galloway. — Dero vaga. 



PLATE 2. 



Fig. 8. Transverse section of the same worm as tliat from which Figure 7 is 

 drawn, but anterior to the plane of separation. X 218. 



Fig. 9. Transverse section of posterior zooid in the region of the pharynx (phy.). 

 Tiie stage is later than that represented in Figures 6-8. The lumen ap- 

 pears as a cavity formed by the splitting of the old entoderm {en'drmA) 

 from the new {en^drmP). 



Fig. 10. Semi-diagrammatic representation of the course of the circumoesophageal 

 connective {cont.crc'oe.) in its relation to the ganglia, tlie muscles, and 

 the lateral line cells {d. In. /.). X 200. 



Fig. 11. Parasagittal section showing the ectodermal thickening on the ventral 

 surface of the budding segment, at a very early stage. X 500. 



Fig. 12. Similar section at a later stage. X 500. (Figures 11, 12, are to be com- 

 pared with Figures 4 and 5.) 



Fig. 13. Part of longitudinal section of normal entodermal layer of intestine, show- 

 ing sub-epithelial cells {sb-e^th.}. X 800. 



Fig. 14. Sagittal section of head of posterior zooid which has been separated from 

 anterior zooid one hour, showing the extent of ectoderm and entoderm 

 in the formation of the mouth and pharynx, in the median plane 

 Ec'drm? marks the boundary between new ectoderm and new ento- 

 derm ; ec'drm}, the boundary between the newly formed ectoderm and 

 the old ectoderm of the mechanically infolded edge of the prostomium, 

 formerly attached to the anterior zooid. X 218. 



