PLATE r. 



Figs. 1-10 show the transition from Surirella ni/assae O. Miill. into 5. malomhae. O. 



Miill. 

 Figs. 11 anrl 12 sliow the transition from Surirella nyassae into S. EngleriO. Miill. 



var. constricta O. Miill. 

 Fig. 13. S. Engleri, var. constricta. 

 Fig. 14. 5. Ein/leri, var. constricta, gigantic form. 



All tlie figures are from microphotographs taken by Mr. A. Hesselbo ; x 300. 



