32 IOWA ACADEMY OF SCIENCES. 



Of the nutrition of plants and animals the previous centuries 

 have little to say. Malphigi inferred that the food of plants 

 was elaborated in the green parts. Marijtte showed that 

 plants form chemical combinations from food material taken 

 from the earth and air. Little more could be done before the 

 discovery of oxygen in 1774, aad the explanation of the move- 

 ment of sap had to wait for the discovery of Osmosis in 1822. 

 Relying upon the work of Lavoisier, who himself experimented 

 upon the respiration of plants and animals. Ingen-Hcuss 

 proved in 1796 that all parts of the plant absorb oxygen and 

 form carbon dioxide, but that the green parts under the 

 influence of sunlight absorb carbon dioxide and exhale oxygen. 

 De Saussaure and Liebig have both been regarded as the 

 founders of this branch of physiology, but they both belong in 

 a later period. It need hardly be stated that animal nutrition 

 was a subject far too difficult for the time. 



Probably the greatest doctrine of all science after that of 

 gravitatioa is Evolution. The idea in some form may be traced 

 to the early Greeks, and it has a place in the discussions of most 

 modern philosophers. It was prominently brought forward, 

 but as a speculation by at least two men of science of the 

 eighteenth century, Buffon and Erasmus Darwin. With neither, 

 however, did the idea advance beyond conjecture or suggestion, 

 and neither seems to have attempted to establish it either by a 

 priori reasoning, or by the marshalling of facts; and the great 

 majority of biologists, therefore, place the origin of the idea 

 as a scientific doctrine at the time of the publication of Lam- 

 arck's Scientific Zoology in 1809. 



To sum up, therefore, we have previously to 1800, a biology 

 of classification, chiefly in the higher orders of plants and 

 animals. We have the beginnings of minute anatomy, the 

 beginnings of theories of reproduction, nutrition and evolution, 

 and the idea of homology as a speculation by Gosthe. There 

 was yet no evolution so far as rega''ds its factors, variation, 

 external influences, heredity; no variation or origin of species 

 in time; no movement and, therefore, properly speaking, no 

 scientifically founded Philosophy of Biology. 



GEOLOGY. 



Geology is a composite of many sciences, and the history of 

 its development is exceedingly complex. Its principles do not 

 admit of ready demonstration by formal syllogisms and Q. E. 



