The Cambridge natural history . urface of the water, andwater through a branchia (see p. 158). Siphonaria (Fig. 57) isalso furnished with a lung-cavity as well as a branchia. Boththese genera may he regarded as in process of change from anaqueous to a terrestrial life, and in Siphonaria the branchia is toa great extent atrophied, since the animal is out of the water, onthe average, twenty two hours out of the twenty-four. In the alliedgenus Gadinia, where there is no trace of a branchia, but only a ^ The result of some experiments by Professor Herdman upon Littorina rudis,tends to show that it
The Cambridge natural history . urface of the water, andwater through a branchia (see p. 158). Siphonaria (Fig. 57) isalso furnished with a lung-cavity as well as a branchia. Boththese genera may he regarded as in process of change from anaqueous to a terrestrial life, and in Siphonaria the branchia is toa great extent atrophied, since the animal is out of the water, onthe average, twenty two hours out of the twenty-four. In the alliedgenus Gadinia, where there is no trace of a branchia, but only a ^ The result of some experiments by Professor Herdman upon Littorina rudis,tends to show that it can live much better in air than in water, and goes far to supportthe view that the species may be undergoing, as we know many species must have under-gone (see p. 20), a transition from a marine to a terrestrial life. It Avas found thatmarked specimens upon the rocks did not move their position for thirty-one successivedays (Pioc. Livcrp. Biol. Soc. iv. 1890, p. 50). - Diminutive of \-Tet?, a comb. 152 RESPIRATION BY THE SKIN. lung-cavity, and in CcrWiidca oMusa, which has a puhuunaiy Fro. 57.—A, SipJin/iariu , P;uiaiiia, the animalcontracted in spirit: gr,sijilional groove on B, Gadinia i)er}i-riana, Sowh., Cldli, shellonly: gr, mark of siphonalgroove to riglit of head. organisation exactly analogous to that of Cycloj)horus^ thisprocess may l)e regarded as practically completed. Eespiration Ijy means of tlie skin, without the development of any special organ, is thesimplest method of breathingwhich occurs in the certain cases, Elysia, Li-mapontia, and Cenia among theNudibranchs, and the parasiticJEntoconcha and Entocolax, noneof which possess breathing organsof any kind, the whole t)utersurface of the l)ody appears toperform respiratory functions. Inothers, the dorsal surface is cov-ered with papillae of varied sizeand number, which communicatewith the heart l)y an elaboratesystem of veins. This is the casewith the greater inunber o
Size: 1873px × 1333px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
