THE NEMATOCYSTS OF EOLTDS 
121 
d. Can the nematocyst content of an eolid be altered by a 
change in diet? 
e. Does a nematocyst-bearing species ever have individuals 
devoid of nettles? 
/. Can the transfer of nematocysts from, coelenterates to the 
cnidophores of eolids be followed in detail? 
The diet of eolids 
The literature is full of testimony alleging the close association 
of eolids and coelenterates. Moreover, eolids have frequent!}^ 
been observed while feeding on their coelenterate neighbors. I 
have often seen them browsing on Tubularia crocea; on Euden- 
drium racemosum; and on actinians. Many species are so trans- 
lucent that their food gives its color to the entire animal, and 
individuals which have fed on the pink heads of Eudendrium, or 
the somewhat paler ones of Tubularia, have the exact tints char- 
acteristic of these hydroids. Careful examination shows that the 
colors are due to undigested food in the alimentary canal and its 
diverticula. 
Identity of eolidian and coelenterate nettles 
As Grosvenor says, ''Those who quote the nematocysts of 
nudibranchs and coelenterates as a striking example of homoplasy 
or convergence, can scarcely be aware of the astonishing complete- 
ness of this assumed convergence." His assertion is supported 
by a considerable number of cases in which the isomorphism ex- 
tends to the minutest details. Wright and Cuenot made similar 
observations. A number of equally striking instances have come 
to m}^ notice, but I shall describe only two. 
Among the sagartias attached in great numbers to oyster shells, 
at Beaufort, X. C, I found one eolid with nematocysts absolutely 
like those occurring in the tentacles of the actinian. The undis- 
charged nettle of sagartia is a small rod in whose long axis lies 
a straight filament. Unexploded capsules answering to this 
