388 Rev. R. T. Lowe on the Respiratory Organs 



while our land Pidmonifera cannot long survive a total immersion in 

 water, certain amphibious littoral MoUusca, the nature of whose respira- 

 tory organs is in question, can do so : and hence that the powers of 

 these animals are certainly, those of the breathing organs are probably, 

 and therefore the structure of the latter also probably, dissimilar. But 

 it is not allowable to infer from this, with anything more than conjectural 

 force, that the breathing organs of the latter are in structure so different 

 from those of the land MoUusca, as is involved in the supposition that 

 they are pectinated, till I have also proved, by similarly conducted ex- 

 periments, that the fluviatile Pidmonifera will, no more than those of 

 the land, survive a total immersion, for an equal length of time with my 

 Pedipedes and Truncatellce, in the fluid they inhabit. And even then, 

 that they are precisely so different as to be actually pectinated, will per- 

 haps after all require little short of anatomical demonstration : for it is 

 possible, that this difference of power may be the result of some dif- 

 ference of organization, or of some apparatus of compensation, existing 

 elsewhere than in the respiratory organs ; analogous to that which the 

 Seal possesses in the large venous sinus of the liver ; or to that which the 

 fcEtus exhibits in the ybramen ovaZe, among Mammalia: the breathing 

 organs themselves remaining the same. The question as to the fluviatile 

 Pulmonifera, however, is a point most easily determined* by any one 

 who can procure live Limncece or Physa;, &c. ; whilst here it is imprac- 

 ticable, or at least difficult, there being only one or perhaps two minute 

 new species of Limncea, and those of extreme rarity, besides ^ncylus 

 Jluviatilis, in the island. I must therefore content myself with com- 

 mending this simple experiment to some of my conchological friends at 

 home, which will serve as a very fair sort of experimentum crucis to 

 my former trials in Madera. If the result satisfactorily determine the 



* Miiller at p. 128 of the Hist. Venn, has an observation on his Buccinum 

 auricula (Linn<Ba auricularia, Auct. rec.) much in point, tending as far as it 

 goes to confirm what I cannot help suspecting may prove to be the fact ; namely 

 that these fluviatile Pulmonif era wiW really be found capable of supporting life 

 when totally immersed. But still, like his other experiments, it is too defi- 

 cient in detail and precision to establish the matter in question. 



