Davknport. — Ciistatella. 



PLATE I. 



Fig. 1. A portion of the lateral rim of a colony. An optical section taken just 

 below the roof of the colony, showing the arrangement of polypides. 

 X 72. 



" 2. Origin of the stolon (I.) from the neck of a mother polypide of about 

 Stage XII. (Fig. 18). Sagittal section of mother polypide. The 

 margin of tiie colony is to the left. X 390. 



" 3. Earliest stage in the origin of a bud from a young mother polypide. 

 Sagittal section. Margin to left, x 390. 



" 4. Origin of a bud from a mother polypide of about the age of that of Fig. 3. 

 Sagittal section. Tiie margin of the colony is to the right of figure. 

 X 390. 



" 5. Sagittal section of a double bud. Margin of colony to the left, x 390. 



" 6. Later stage in bud formation of same type as Fig. 4. Sagittal section. 

 X 390. 



" 7. A part of the right side of a polypide of a stage of development interme- 

 diate between those of Figs. 19 and 73. Seen from the sagittal plane. 

 The cut surface lies to the right of the sagittal plane, and passes 

 through the orifice of the right lophophore arm. The alimentary tract 

 thus lies immediately above the plane of the paper, x 150. 



