136 
OTTO C. GLASER 
that there exists in eolidsan anti-body capable of neutralizing hyp- 
notoxin, provided this substance is not introduced in too large 
quantities, or in a variety to which the anti-body is not adapted. 
If this sort of immunity exists, then the total ''immunity" of 
an eolid to a particular type of nematocyst is due in part to the 
various factors which prevent the mollusc from being punctured; 
in part to acclimatization, ph34etic or otherwise, to the mechanical 
effects of such punctures as are made ; and finally to the neutrali- 
zation of the small quantities of hypnotoxin introduced. 
With the demonstration that immunity exists, but is relative 
and dependent on several distinct factors, the way is paved for a 
consideration of the origin of the nematocyst-storing habit. 
The indigestibility of the nettles renders their elimination neces- 
sary. One way in which this is accomplished is by voidance with 
the faeces; another by voidance through the cnidopores. Why this 
second method should have developed is difficult to determine. 
According to Hecht ('96), Calma glaucoides is a typical eolid 
except in two respects; it has neither cnidophorcs nor nematocyst s. 
Calma cavolinii, the only other member of the genus has cnido- 
phores filled with nettles. As C. glaucoides in all probability did 
not branch off from the common eolid stock before the introduc- 
tion of nettles, and as its habit of feeding upon the eggs and 
embryos of shore fish, such as Cotta, is, with equal probability 
secondary, it seems likely that the abandonment of the nemato- 
cyst habit is quickly followed by degeneration of the accessory 
organs of elimination. If this be true, one may infer that the 
presence of nematocyst s influences the production of cnidophores, 
much as an insect sting may bring on, in a plant, the formation 
of galls. 
I do not know what it is in nematocysts that renders their 
prompt removal from the digestive tract proper, desirable, nor 
whether the immediate end, whatever it be, is accomplished 
by the means employed. That elimination, or at least storage, 
is somehow useful, while not absolutely proved, is certainly prob- 
able, for the idea that it is profitless or harmful is difficult to 
harmonize with the complexity of the structures and processes 
involved. It must be borne in mind that a ciliated canal makes 
