PLATE XXII. 
Figs. 1-4. — Perisiphonia filicula (p. 44). 
Fig. 1. — A colony ; natural size. 
Fig. 2. — Distal end of a pinna ; magnified 25 diameters. The axial and peripheral tubes 
are partly separated from one another after maceration in caustic potash. 
Where the peripheral tubes still remain in their natural position, the distal 
extremities of the hydrothecge are seen projecting from between them. 
Sarcothecse are seen to be carried by the outer peripheral tubes. 
/ • 
•Fig. 3. — Portion of the stem after maceration in caustic potash ; magnified 25 
diameters. The axial tube has been nearly freed from the surrounding 
peripheral tubes. The origins of the pinnae from the main stem are seen. 
Fig. 4. — Outline of hydrotheca, showing a sarcotheca springing from its peduncle. 
