32 BRITISH MARINE TESTACEOUS MOLLUSCA: 
these points are little better than hypotheses, and rest on 
unsound demonstrations. It is well known that the mind, 
deeply intent on the examination of the very minute objects 
of natural history, when jaded and exhausted by the pressure 
of high microscopical powers, often deceives itself, and from 
preconceived impressions, idealizes and fancies it sees objects 
that have only an imaginative existence, and strongly distorts 
real ones through optical illusion. 
We admit that in the lower Invertebrata there is no mecha- 
nism for sustentation, circulation, and respiration, of the com- 
plex and advanced character of the Mollusca, as heart, auricles, 
arteries, and vems; but though these inferior grades do not 
present the strict homologues of these organs, we think that 
there are in them analogical substitutes, which rescue the 
simplest of these beings from the confusion and unnatural 
admixture of organs and functions that have not the commu- 
nity which authors have ascribed to them. 
Though a heart and circulatory vascular structure cannot 
be demonstrated in the minuter, and even in some of the 
largest of the Radiata, we nevertheless believe that they exist, 
as well as a distinct visceral cavity and canaliferous walled 
recipient for the aliments, and that the two mechanisms ve 
not otherwise connected, except by the former receiving from 
the laboratories of the latter the influences and elements to 
invest the blood with the power of sustaiming life, after it has 
received the impress and interchange of the gases with those 
of the exterior or interior fluid aérating elements by endos- 
mose or exosmose, and thus establish the vital principle. 
And further, we are of opmion that muscles and nerves are 
present in the lowest of these organisms to excite motion and 
sensation to an extent commensurate with their wants. 
On this head we cannot help quoting a passage of ours m 
the ‘Annals of Natural History,’ vol. v. p. 161, N.S., in a 
paper on the Foraminifera :— 
“On the question of the nervous and muscular influences, 
which Lamarck only admits, as independent of sensation and 
interior sentiment, in his apathetic animals, amongst which 
are the Polypi, I must be allowed to make a few observations, 
