388 Rev. R. T. Lowe on the Respiratory Organs 
while our land Pulmonifera cannot long survive a total immersion in 
water, certain amphibious littoral Mollusca, 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 Mollusca, as is involved in the supposition that 
they are pectinated, till I have also proved, by similarly conducted ex- 
periments, that the fluviatile Pulmonifera will, no more than those of 
the land, survive a total immersion, for an equal length of time with my 
Pedipedes and Truncatelle, 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 
foetus exhibits in the foramen ovale, among Mammalia: the breathing 
organs themselves remaining the same. The question as to the fluviatile 
Pulmonifera, however, isa point most easily determined* by any one 
who can procure live Limnee or Physe, &c.; whilst here it is imprac- 
ticable, or at least difficult, there being only one or perhaps two minute 
new species of Limnea, and those of extreme rarity, besides Ancylus 
fluviatilis, 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. Verm. has an observation on his Buccinum 
auricula (Linnea 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 Pu/monifera will 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. 
