Hi, J. Clark on Lucernaria. 353 
Were the above-mentioned features in the organism of Lucer- 
haria alone to be taken into account, there could be no a 
Si 
ype of geni 8 
have no — in all pe class of a But there are 
in the first se to the hydra-like form of Lucernaria, and i 
comparatively stiff and hydroidal tentacles, evidently indicating 
- aperture of the cell, and pressing closely against noite Rye face of the cell wall it 
forms $ a close coil which terminates at the end opposit the mouth of the introver- 
; jepiach eae is Be h 
broader than the cylindrical portion, and rapidly tapers into a Bac trih 
thread. The oval part of the shaft is endowed with three me poms. spiral 
megs sete, which number about a dozen in each row. The se ompara- 
x vely large, and i in length wes two ore a ponior  esanga ag that part of 
e shaft from which they project. Eac one turn about the 
and terminates as if in continuation of the. “arigtes of the trihedral thread. There 
* Not the least trace > - or projections of any kind upon the trihedral thread, 
3 
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hom 
& 
o 
8 
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s. 
i) 
c 
2 
4. 
or 
a 
3 
BS. 
bs =) 
oO 
- 
bone] 
4 
oo 
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= 
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gradua perfectly s 
€ angles of the ibeasa appear, at first ae as if they might be spiral 
ows of sete, but a most careful and prolonged examination, with one of Spencer’s 
1 objectives, convinces me that rey 8 are truly the angles of a twi 
of the cell. The other kind of nettling cell is much more sim mple i in structure, 
yet more remarkable. The seer shaft is very slender, in fact no larger t than 
“a rest of or often it does not project into the axis cylindrico-o 
but presses ¢ othe side of of the latter, and extends four —_ of the wags to its 
Curved sweep nearly to the aperture of the cell, fr ethan i again Per with 
long sweep, which is repeated eight to ten eile until the inner face of the 
ir a close coi i ise, i 
~Xcept at the end, where it cae slig htly and seas in a blunt tip. The cell 
itself, when retroverted, is sensibl diminished in size, and narrows rapidly into the 
filamentary portion. It would se a a re perfectly incontestable that, 
_ 88 the cell diminishes in size with the expulsion of the thread, it forms the propell- 
: ‘98 power, and, by the contraction of its wall, forces its contents outward, 
