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OTTO C. GLASER 
tracts its disc when assaulted, it is devoured in its least dangerous 
state. The outcome of the two experiments is thus very different. 
It follows from this that even an absolute immunity to the nema- 
tocysts of one ccelenterate does not insure immunity against 
those of another. The absolute immunity itself, however, does 
not exist. It has been said by several writers that eolids showing 
evidence of having been punctured either from without or within 
by the sort of nettles in which they normally traffic are unknown. 
Fig. 11 represents a cross section through a ceras taken from an 
Fig. 11 Cross section through the base of a cnidophore in which intra-ceratal 
explosions have taken place. 
eolid feeding normally on Aiptasia. The particular section is by 
no means representative, and gives a very inadequate idea of the 
number of discharges which has occurred in this appendage. 
My reason for choosing it is the ease with which the individual 
filaments can be traced to their capsules. Other sections contains 
inextricable snarls of threads. 
Immunity, therefore, is relative and depends on several interest- 
ing details. It is not unlikely that phyletic as wtll as individual 
- acclimatization plays a role; more important, however, are the 
reactions of ccelenterates to eolids, and most important the nema- 
