POLYGYRA ALBOLABRIS AND LIMAX MAXIMUS 311 



PLATE 28 

 Fig. 



1 A group of cells after segmentation, greatly enlarged. 



2 A group of cells at a later stage; the larger and smaller cells 



grouped In polygonal masses, and distorted from mutual 

 pressure, greatly enlarged. 



3 The cells liberated from one of the polygonal masses^ show- 



ing their true form, greatly enlarged. 



4 The primitive kidney showing the cells and their calcareous 



concretions, greatly enlarged. 



5, 6 Groups of cells from the position indicated by the lettering 

 5 and 6, figure 5, plate 26, greatly enlarged. The latter 

 containing calcareous concretions as in the "primitive 

 kidney." 



7-13 Showing the gradual development of the shell, x 30. 

 14 The fully formed shell, dorsal view, x 2. The under side of 

 the shell has very much the appearance represented in 

 figure 13. 



