TWO SPECIES OF HYDRACTINIA 
475 
HYDRACTINIA SODALIS 
Fig. 1 A colony without polyps, with the enclosed gastropod shell (Columbella 
sp.) on one side. Nat. size. 
Fig. 2 A colony without polyps on a gastropod shell of one of the Buccinidae, 
Nat. size. 
Fig. 3 Transverse section of the chitinous skeleton at right angles to the 
mouth of the shell. 60 diam. The upper side is the outer. 
Fig. 4 Longitudinal section of spine, axial part. 60 diam. 
