CLASSIUCATION OF ANIMALS. 5 



present in the alga3, the fungi, and almost all cryptoganiia. On 

 the other hand, it has been shown by Scliraidt * that some animal 

 tissues are binary compounds, as e. g., the mantle of the Frustulice and 

 the thick cellular tunic of the Ascidice. 



Thus whilst it may be affirmed in a general way that plants decom- 

 pose and animals recompose carbonic acid, the one fixing the carbon 

 and yielding the oxygen, the other freeing the carbon in combination 

 with oxygen taken from the atmosphere; that the plant exhales 

 less water, and the animal more water, than it imbibes ; that 

 whilst the plant ^are« ammonia and uses its elements for the produc- 

 tion of organic compounds, the animal sets free azotised substances 

 which speedily resolve themselves into ammoniacal compounds; — the 

 beneficial antagonism can only be predicated in a general way of the 

 more complex or typical members of each kingdom respectively, and 

 will not serve as a rigorous basis of definition in the lower approxi- 

 mated forms where the aid of the chemist has been most wanted for 

 that purpose. 



The physiologist has asserted that plants alone can subsist on 

 inorganic matter, and that animals depend upon plants for combining 

 the elements into binary and ternary compounds essential to animal 

 support, f And this also is in some degree true : the lichen that 

 first clothed the granite rock must have converted the inorganic 

 elements into cellular tissue. Animals, as a general rule, subsist on 

 vegetable or on animal matter, or on both. But no proof has been 

 given that the Frustulice and other astomous polygastria, which 

 separate oxygen in excess, do not effect this by reducing the carbonic 

 acid of the atmosphere, and fixing the carbon, in order to produce 

 their fats and hydrates of carbon : or that they do not, in like 

 manner, assimilate their ammonia either directly, or by taking the 

 nitrogen of the atmosphere into the required combination ; and so by 

 its subsequent combination with the elements of the fats and hydro- 

 carbonates, produce their proteine compounds and albuminates. Still 

 less proof or probability have we that the typical or higher organised 

 forms of vegetation could flourish without the support of decaying 

 organised tissues, superadded to the air and water. 



Ehrenberg | seems to have rested from his analysis of the distinc- 

 tion between plants and animals, on arriving at considerations offered 

 by the generative function, and accordingly refers the " DesmidicB," 

 " Diatomacece" and " Closteruc " to tlie animal kingdom, which he 

 characterizes by "the power of increase by voluntary division," super- 



* IX. p. 34. t X. Vol. i. p. 2. t XI. p. 88. 



B 3 



