1833.] SEA-PEN. 99 



treme heat, Mas 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 aestivation, 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 Avater, they were peopled by numerous full-grown 

 shells and beetles, which must have been lying dormant. Hum- 

 boldt has related the strangle accident of a hovel havino: 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 

 M'ith water." 



I will only mention one other animal, a zoophyte (I believe 

 A'^irgularia 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 tlie 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. AYhen 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 tlie 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. Each poly- 

 pus, though closely united to it-s bretliren, 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 compartrnents of the extrernitj-, 



