PLATE XVIII. 



FIG. 



1. Membranipora monostachys, p. 131 ; nat. size, show- 

 ing the linear habit of growth. 



2. , a colony, inckiding one of the rudi- 

 mentary cells. 



3. , var. FOSSARiA. 



4. , var. FOSSARIA : two zooecia, viewed 



sideways, 



5. Membranipora membranacea, p. 140. 



G. , with a number of abnormal cells ("tower- 



zocecia^^ of Nitsche). 



7. Membranipora hexagona, p. 143. After Busk. 



8. ScHizopoRELLA HYALiNA/ p. 271 ] a colony with 



suborbicular orifice. 



9.  , with the ooecia borne on imperfectly 



developed cells. 



10. , var. with hyaline walls and the lower 



margin of the orifice deeply sinuatcd. Sec Plate 

 XLV. figs. 2 and 3. 



