EXPLANATION OF PLATE IIL 



Figs. I, 2. — Typical form of Metridium schillerianum, xi (after 

 Stoliczka). 



Fig. 3. — Pond race of Metridium schillerianum in a contracted con- 

 dition, X I {ad nat.). 



Fig. 4. — Transverse section of wall of column of M. schillerianum 

 var. exul in the region of stomodseum (magnified). 



Fig. 5. — Transverse section of wall of column of the typical form of 

 M . schillerianum (at the same magnification as fig. 4). 



Fig. 6. — Ditto (less highly magnified). 



Figs. 7-12. — Stages in the development of the violet bodies of M. 

 schillerianum (enormously magnified). Figs. 7-11 

 are diagrammatic, 



ii6.=ectoderm : ew.=endoderm : m.=mesoderm. The endo- 

 derm in the figures is apparently divided into two layers, but this 

 is due to the almost complete absence of zooxanthellse in the 

 basal part of the cells. 



