376 ORGANIC EVOLUTION CONSIDERED 



the characters of individual animals and plants. These 

 influences fall naturally into two classes, viz., the 

 physico-chemical (molecular,) and the mechanical 

 (molar). The modifications so presented are sup- 

 posed to be the result of the action of the causes in 

 question, continued throughout geological time." 

 He gives the names Physiogenesis and Kinetogenesis 

 to the above causes. "In the animal kingdom we 

 may reasonably suppose that kinetogenesis is more 

 potent as an efficient cause of evolution than physio- 

 genesis." * 



Under physiogenesis the author shows the effects 

 of light and of certain kinds of food in modifying 

 the colors of a few animals; also, the effects of 

 changing the saltness of water on two or three spe- 

 cies; and, finally, he considered the blindness of ani- 

 mals that live in caves. 



If all that he claims in this chapter is true, yet it 

 has but little bearing on the question of evolution. 

 Change of color has little, if anything, to do with 

 change of structure, and loss of vision by disuse can- 

 not explain the origin of eyes. 



The chapter on Kinetogenesis occupies 140 pages. 

 The author, relying on this as the principal cause of 

 variations, attempts to explain the origin of organs 

 and the great changes which have, according to evo- 

 lution, taken place in the structure of animals. 



I can only refer to a few parts of this chapter, 

 which will give some idea of the author's method. 



As to the origin of lungs, he says: " The habit of 

 holding in the oesophagus large quantities of air while 

 engaged in seeking food in foul water, or on land, on 

 the part of vertebrates which normally oxygenated 

 the blood by means of gills, was probably the mechan- 

 ical cause of the development of a pouch, and after- 



*Page 225. 



