378 CHARLES IL. BOULENGER. 
Fie. 9.—The three types of nematocysts:—a. The large oval form in the 
unexploded condition. 4. The same with the thread everted, only two of the 
three large barbs can be ‘seen. ec. The cylindrical nematocyst with spirally 
coiled thread. d. The pip-shaped form, unexploded, to show thread coiled 
round the transverse axis. e. The same with thread everted. Zeiss obj. F, 
oc. 2. 
Fie. 10.—Transverse section through a stomach diverticulum and part of 
the umbrella of an adult medusa. The cavities of the diverticulum and radial 
canal are continuous, but the endodermal linings of the two structures are 
quite distinct. x about 60. 
Fic. 11.—Similar to Fig. 10, but the section is cut through the distal 
extremity of the diverticulum where its cavity is separate from that of the 
radial canal, 
