BRIGHTWELL, ON RHIZOSOLENIA. 95 
3. Rh. setigera.— Frustule five to fifteen times longer than 
broad ; transverse lines obscure ; terminal bristle as long as 
the frustule ; colourless, of glassy transparency. 
In Ascidize with the two former species. (Mr. Norman.) 
In Noctiluce. (Col. Baddeley.) In Salpz. (Dr. Wallick.) 
This species is distinguished by its extreme delicacy, and 
by the great length of the terminal bristle. (Pl. V, fig. 7). 
4. Rh. alata—Terminal process alate, recurved, blunt; 
colour chestnut brown. 
In Ascidize with Rh. styliformis. (Mr. Norman.) 
This delicate little species, which bears some resemblance to 
a pipe fish, and might have been called “ sygnathoides ” differs 
frout all the others by its blunt, turned-up nose, and its small 
but conspicuous appendages to the terminal process (Pl. V, 
fig. 8). 
In most of the above species, self-division has been ob- 
served. It takes place in or near the centre of the frustule, 
and has the same indefinite character as in Rhabdonema and 
Striatella. The rings of the Rhizosoleniz appear equivalent 
to the annuli in these genera, but, instead of being perfect 
and united by flat surfaces, they are united at acute angles, 
and carry out the frustule to an almost indefinite length. 
The process of self-division is therefore truly diatomaceous. 
Two new calyptriform valves are gradually formed within a 
connecting membrane, as is seen in our PI. V, figs. 6, 7, a, 6. 
These eventually separate, when the old frustule becomes 
two, each division having a new calyptriform end. 
In the genus Isthmia, the frustules of which are trapezoi- 
dal, one valve having a produced angle, we see some resem- 
blance to the Rhizosoleniew, and this would be much 
increased by supposing an Isthmia carried out to ten times 
its normal length, and self-division taking place in the 
centre, as seen in the central fig. in pl. xlvii, ‘ Smith’s 
Brit. Diatom.’ 
In specimens of Rh. setigera a motion has been observed 
resembling that of many of the Diatomacez, the frustule 
proceeding forward in a jerking, tremulous manner, and then 
retrograding. 
Large numbers of Rhizosolenia have been detected in the 
stomachs of Salpze, and they have also been observed floating 
free in the ocean in warm latitudes, their appearance being 
that of little confervoid flakes of exquisite delicacy, but of a 
sufficient aggregation of filaments to be seen by the naked 
eye. The mass appeared (probably from the endochrome) 
of a faint, evanescent, ochraceous colour. 
