250 WM. A. KEPNER AND JOHN F. BARKER. 



4. The fact that this method of handling- the nematocysts 

 demands considerable work on the part of the endodermal cells 

 and, in each case of a discharged nematocyst, the death of a 

 cnidophage or mesodermal cell further suggests that it is all 

 done with reference to use. 



5. Microstoma incurs danger in attacking Hydra; for it is 

 frequently stung and sometimes killed by the polyp. This too 

 suggests that the Microstoma attacks Hydra for some peculiar 

 end. 



6. The Microst.oma is able to draw nematocysts with which 

 Hydra has stung it from its body, without suffering a rupture 

 as does Stenostoma. 



7. Microstoma with a few nematocysts attacks Hydra within 

 a little time. 



8. Microstoma having many nematocysts does not readily 

 attack Hydra. The contrast between 7 and 8 suggests that 

 Microstoma attacks Hydra not for food ; but for its nematocysts. 



9. The alimentary canal of a recently fed Microstoma, that 

 has few nematocysts, may egest the " flesh " of Hydra and re- 

 tain its nematocysts. 



10. The alimentary canal of a Microstoma that has many 

 nematocysts and is hungry, may egest the nematocysts of Hydra 

 and retain the " flesh " of the polyp. The contrast between 9 

 and 10 suggests that Micro stf>ma seeks primarily the nemato- 

 cysts of Hydra. 



11. The discharge of the nematocysts is a double process, 

 involving (i) an oscillation to and fro of the nematocyst within 

 its cnidophage, and (2) the actual discharge. The first phase 

 may be carried on without being followed by the second phase. 

 Neither of these has ever been seen except when some active 

 body, like the experimenter's needle or an animal has brushed 

 along the surface of Microstoma. This, too, suggests that the 

 nematocysts are for use. 



12. Finally Microstoma actually stings and paralyses other 

 animals with the nematocysts it has appropriated from Hydras 

 that it has eaten. 



