32 BEITISH 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 veins; 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 are 

 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 sustaining life, after it has 

 received the impress and interchange of the gases with those 

 of the exterior or interior fluid aerating elements by endos- 

 mose or exosmose, and thus establish the vital principle. 

 And further, we are of opinion 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 in 

 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, 



