HABITS OF ANIMALS. 93 



these and the so-called lungs of the air breathing Mollusks, 

 whose aerial respiratory cavity is only a modification of 

 the peculiar kind of gills observed in other Mollusks. 

 Examples might easily be multiplied. I will, however, 

 only allude further to the alimentary canal of Insects and 

 Crustacea with its glandular appendages, formed in such 

 a different way from that of Vertebrata, or Mollusks, or 

 Eadiata, to their legs and wings, etc., etc. I might allude 

 also to what has been called the foot in Mollusks, did it 

 not appear like pretending to suppose that any one still 

 entertains an idea that such a name implies any similarity 

 between their locomotive apparatus and that of Verte- 

 brata or Articulata ; and yet the very use of such a name 

 misleads the student; and even some of the coryphees of 

 our science have not freed themselves from such and 

 similar extravagant comparisons, especially with reference 

 to the solid parts of the frame of the lower animals. 1 



Tins identification of functions and organs was a natural 

 consequence of the prevailing ideas respecting the in- 

 fluence physical agents were supposed to have upon or- 

 ganized beings. But as soon as it is understood how 

 different the organs may be which perform the same func- 

 tion in animals, organization is at once brought into such 

 a position towards physical agents as to make it utterly 

 impossible to maintain the idea that there is any genetic 

 connexion between them. A fish, a crab, a mussel, living 

 in the same waters, breathing at the same source, should 

 have the same respiratory organs, if the elements in which 

 'these animals live had anything to do with shaping their 

 organization. I suppose no one can be so short-sighted 

 as to assume that the same physical agents acting upon 



1 CARUS (C. G.), Von den Ur-Thei- tes; Leipzig, 1828, 1 vol. fol., p. 61- 

 len des Knochen- und Schalengems- 89. 



