ANNOTATIONS AND ADDITIONS. 61 



belong to the division of the Pentastomes. (Budolphi, 

 Entozoorum Synopsis, p. 124 and 434.) It inhabits the 

 ventral cavities and wide-celled lungs of a species of Cro- 

 talus which lives in Cumana, sometimes in the interior of 

 houses, where it pursues the mice. Ascaris lumbrici 

 (Gozen's Eingeweidewiirmer, Tab. iv. Fig. 10,) lives 

 under the skin of the common earthworm, and is the 

 smallest of all the species of Ascaris. Leucophra nodulata, 

 Gleichen's pearl-animalcule, has been observed by Otto 

 Friedrich Muller in the interior of the reddish Nais litto- 

 ralis. (Muller, Zoologia danica, Fasc. II. Tab. Ixxx. a e.) 

 Probably these microscopic animals are again inhabited 

 by others. All are surrounded 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 Fourcro/s 

 experiments the swimming bladders of fish appeared to 

 contain an air entirely deprived of oxygen. Erman's 

 experience and my own shew, however, that fresh-water 

 fishes never contain pure nitrogen iii their swimming 

 bladders. (Humboldt et Prove^al, sur la respiration des 

 Poissons, in the Eecueil d'Observ. de Zoologie, Vol. ii. p. 

 194-216.) In sea-fish as much as 0*80 of oxygen has 

 been found, and according to Biot the purity of the air 

 would appear to depend on the depth at which the fish live. 

 (Memoires de Physique et de Chimie de la Societ6 d'Arcueil, 

 T. i. 1807, p. 252-281.) 



