1833.] SEA-PEN. 99 
treme heat, was sufficient to awake all orders of animated beings. 
This shows how nicely the stimulus required to arouse hybernat- 
ing animals is governed by the usual climate of the district, and 
not by the absolute heat. It is well known that within the 
tropics, the hybernation, or more properly estivation, of animals 
is determined not by the temperature, but by the times of 
drought. Near Rio de Janeiro, I was at first surprised to ob- 
serve, that, a few days after some little depressions had been 
filled with water, they were peopled by numerous full-grown 
shells and beetles, which must have been lying dormant. Hum- 
boldt has related the strange accident of a hovel having been 
erected over a spot where a young crocodile lay buried in the 
hardened mud. He adds, ‘‘The Indians often find enormous 
boas, which they call Uji, or water serpents, in the same lethar- 
gic state. To reanimate them, they must be irritated or wetted 
with water.” 
I will only mention one other animal, a zoophyte (I believe 
Virgularia Patagonica) a kind of sea-pen. It consists of a thin, 
straight, fleshy stem, with alternate rows of polypi on each side, 
and surrounding an elastic stony axis, varying in length from 
eight inches to two feet. The stem at one extremity is truncate, 
but at the other is terminated by a vermiform fleshy appendage. 
The stony axis which gives strength to the stem may be traced 
at this extremity into a mere vessel filled with granular matter. 
At low water hundreds of these zoophytes might be seen, pro- 
jecting like stubble, with the truncate end upwards, a few inches 
above the surface of the muddy sand. When touched or pulled 
they suddenly drew themselves in with force, so as nearly or 
quite to disappear. By this action, the highly elastic axis must 
be bent at the lower extremity, where it is naturally slightly 
curved ; and I imagine it is by this elasticity alone that the 
zoophyte is enabled to rise again through the mud. Lach poly- 
pus, though closely united to its brethren, has a distinct mouth, 
body, and tentacula. Of these polypi, in a large specimen, 
there must be many thousands ; yet we see that they act by one 
movement: they have also one central axis connected with a 
system of obscure circulation, and the ova are produced in an 
organ distinct from the separate individuals.* Well may one be 
* The cavities leading from the fleshy compartments of the extremity, 
