G. ELECTRA. 53 



Their substance is almost wholly membranous and 

 flexible. Colour generally a deep brown. Their size 

 never exceeds eight centimetres. The only species yet 

 known belonging to this genus is often met with on the 

 marine productions of the Mediterranean ; they are 

 found attached to plants, polypidoms, and rocks. 



Pherusa tubulosa. Oblong, tubular, and pro- 

 jecting cells, having their opening on one surface. — 



Plate 2. fig. 1. a. B. C. 



ELECTRA. 



Polypidoms branching; cells campanulated, ci- 

 liated on their border, and verticillated. 



This genus consists of but a single species, whose 

 cells are verticillated round a pulpy centre, or adhere 

 to some Thalassiophyte, usually cylindrical. The 

 rings are in general so close as to make them appear 

 imbricated. 



The Electra is very common in the European seas ; 

 when the polypi are alive, their colour is a red-violet 

 of greater or less brilliancy; but when exposed to air 

 and light, it becomes an earthy white. 



VERTICILLATE. 



Electra verticillata. Cells campanulated, ci- 

 liated in their borders, and placed in rings one above 

 the other. — Plate 2. fig. a. B. 2. 



European seas. 



