On Cejohalosiphorif &g. By Dr. C. T. Hudson, 169 
processes whatever. There were a few faint transverse wrinkles 
just as there are in ordinary Melicertans. 
Cephalosi^hon was not my only prize. I found attached to tlie 
same weed ( — Anacharis alsinastrum — ) clusters of long thin 
brown tubes which at first I thought to be those of Ce^Jialosiphon. 
They proved however to contain a curious infusorion which I 
believe to be new, and which I have named from its frequently 
assumed corkscrew shape, and from its rows of cilia used like 
banks of oars, Archimedea rernex. It really makes its own 
tube ; for I have seen very young specimens in tubes just begun, 
and I have left a group of tubes each with its full-grown Archi- 
medea in it, and after two days have found them still with their 
inhabitants inside them, and each tube lengthened by about y^^^- 
of an inch. The full-grown Archimedea is about of an inch, 
and the longest tube I have met with is of an inch. The 
tube of course is far too long for its inhabitant, who as a rule 
lives in the top of it, though occasionally it backs down the tube 
nearly to the bottom. When inside the tube the animal is extended 
to its full length as in Fig. 2, where a is the ciliated front down 
which a groove ciliated on both sides leads to the entrance of the 
mouth d. On protruding from its home it first remains straight 
quivering its cilia : then, if not alarmed by any shake, or by any- 
thing passing, it thrusts quite half its body from its tube, and 
twists it up into the screw-like form seen in Fig. 3. 
On watching the groove, along the edges of which the cilia are 
in full action, tiny atoms may be seen hurried along to the mouth : 
tap the table, and Archimedea flashes down the tube, quick as a 
serpula ; and if it is in the upper and more transparent end it may 
be seen moving itself gently to and fro as if hesitating whether 
to return to the aperture or to seek a safer refuge down below* 
These are very tantalizing creatures, for they readily desert 
their tubes ; and in spite of all my care I frequently found every 
tube empty after the third or fourth day's captivity. Under 
ordinary circumstances it is a great piece of good luck when a 
tube-maker leaves its tube, as then the observer gets a capital 
chance of making out points of structure that could not be seen 
when the animal was encased ; but Archimedea's tube is so frail, 
and the animal so shy, that the leaf it is on must be transferred to 
the glass cell on the stage of the microscope with the least possible 
handling ; and as the leaf is broad the cell must be so too, so that 
when the creature swims out of its tube (as I have seen it do) it 
is almost impossible to keep in the field for more than a few seconds. 
I tried the heroic method of scraping a group of tubes off the leaf 
on to my compressorium, and after many failures did at last get 
one animal out alive and uninjured, as well as free frOm the debris 
of the tubes, the rubbish on the leaf, &c., &c. : all of which would 
