52 STRETHILL WRIGHT, ON THE EOLID. 
and fitting closely on the larve, which appeared to be im- 
bedded in the longitudinal folds of the highly developed 
endoderm. Mr. Hodge supposes that the larvee, at a very 
early stage, are swallowed by ordinary alimentary polyps 
of the Coryne, and carried through the tubes of the cceno- ~ 
sarc until they arrive at a part which is about to become a 
polyp, which thereupon has its destination altered. And 
I think there can be little doubt that his surmise is correct, 
as in Coryne the Pycnogon sacs, in all stages of development, 
are not only destitute of tentacles, but are, according to 
Professor Allman, covered by a layer of the chitinous poly- 
pary or scleroderm. Such a mode of nidification, however, 
could not take place in Hydractinia, the ccenosarcal tubes 
of which are of exceedingly small calibre. Accordingly we 
find that the Pyenogon sacs in this zoophyte are formed, not 
by the arrest or change in development of an immature polyp, 
but by the degeneration of a tentacled polyp previously per- 
fect. 
Perhaps I ought to mention here that globular sacs are 
occasionally found in place of the polyps in Coryne glanduiosa, 
Dalyell. These are destitute of scleroderm, and lined with 
a very dense brown endoderm, arranged in somewhat reticu- 
lated folds. As far as I observed, they were empty, and, by 
constantly undergoing alternate processes of dilatation and 
contraction, appeared to influence the circulation of the 
zoophyte. Itis possible that minute Pyenogons may have 
existed in these sacs. 
On the Urticatine Finraments of the Eoup2. 
By T. Srreruitt Wricut, M.D. 
In the second volume, new series, of this Journal, p. 274, 
is contained a translation of a paper, by Dr. Bergh, ‘“ On the 
existence of Urticating Filaments in the Mollusca.” As 
neither Dr. Bergh nor his translators appear to be aware that 
anything has been written on these bodies in Great Britain 
since the observations of Messrs. Hancock and Embleton 
were published, I am induced to lay before the readers of this 
Journal an abstract of a paper read by me to the Royal 
Physical Society of Edinburgh, on the 22nd of December, 
1858, and published in their ‘ Proceedings,’ containing obser- 
vations “On the Cnide or Thread-cells of the Eolide,” 
which I have since confirmed by repeated experiments. 
