266 PHYSIOGNOMY OF PLANTS. 



that in living animals the evolution of light depends on an irritation 

 of the nerves. I have seen an Elater noctilucus which was dying, 

 emit strong flashes of light when I touched the ganglion of his fore 

 leg with zinc and silver. Medusae sometimes show increased bright- 

 ness at the moment of completing the galvanic circuit. (Humboldt, 

 Relat. Hist. t. i. pp. 79 and 533.) 



Respecting the wonderful development of mass and power of in- 

 crease in Infusoria, see Ehrenberg, Infus. s. xiii. 291 and 512. He 

 observes that " the galaxy of the minutest organisms passes through 

 the genera of Vibrio and Bacterium, and that of Monas" (in the 

 ktter they are often only ^-^-^ of a line), s. xix. and 244. 



( 6 ) p. 230 " Which inhabits the large pulmonary cells of the rattle- 

 snake of the tropics" 



This animal, which I formerly called an Echinorhynchus, or even 

 a Porocephalus, appears on closer investigation, and according to the 

 better-founded judgment of Rudolphi, to belong to the division of the 

 Pentastones. (Rudolphi, Entozoorum Synopsis, pp. 124 and 434.) 

 It inhabits the ventral cavities and wide-celled lungs of a species of 

 Crotalus which lives in Cumana, sometimes in the interior of houses, 

 where it pursues the mice. Ascaris lumbrici (dozen's Emgeweide- 

 wiirmer, tab. iv. fig. 10) lives under the skin of the common earth- 

 worm, and is the smallest of all the species of Ascaris. Leucophra 

 nodulata, Cleichen's pearl-animalcule, has been observed by Otto 

 Friedrich Miiller in the interior of the reddish Nais littoralis. (Mul- 

 ler, Zoologia danica,, fasc. ii. tab. Ixxx. a e.) Probably these 

 microscopic animals are again inhabited by others. All are sur- 

 rounded by air poor in oxygen, and variously mixed with hydrogen 

 and carbonic acid. Whether any animal can live in pure nitrogen is 

 very doubtful. It might formerly have been believed to be the case 

 with Fischer's Cistidicola farionis, because according to Fourcroy's 

 experiments the swimming bladders of fish appeared to contain an 

 air entirely deprived of oxygen. Erman's experience and my own 

 show, however, that fresh-water fishes never contain pure nitrogen in 

 their swimming bladders. (Humboldt et Provenal, sur la respira- 

 tion des Poissons, in the Recueil d'Observ. de Zoologie, vol. ii. pp. 

 194-216.) In sea-fish, as much as 0.80 of oxygen has been found, 



