August 2, 1895.] 



SCIENCE. 



125 



doctrine of use and disuse of Lamarck, 

 precisely defined and demonstrated. 



The cause of the movements of organic 

 beings are various. The best known are 

 conscious states, as hunger, cold, heat, and 

 various other sensations ; some of them of 

 higher mental grade, as fear, anger, etc. 

 Movements by the lowest animals, as that 

 drop of jelly, the amoeba, appear to be the 

 result of sensations, but owing to the sim- 

 plicity of the structure, it is easy to doubt 

 that this can be the case. It is, however, 

 impossible at present to assign any other 

 cause to some of the movements even of 

 the amoeba, although it must be admitted 

 that our knowledge is slight. The phenome- 

 non of heliotropism, for instance, when 

 these simple creatures leave the dark and 

 crowd into light places, cannot be shown to 

 be due to chemical or physical causes only. 

 They seek oxygen, which is more abundant 

 where sunlight penetrates, but they have 

 to be aware that they need it, and must 

 have some knowledge of the fact when 

 when they get it. This indicates a low 

 grade of consciousness. But it is conscious- 

 ness, nevertheless. But whatever may be 

 the state of the case with the amoeba, we do 

 not have to ascend far above it in the 

 zoological scale before we meet with clear 

 evidences of the presence of sensation. 

 Hunger, for instance, is a form of conscious- 

 ness, although it is due to a physical condi- 

 tion. 



The result of progressive evolution in 

 animals is developed mechanism of motion, 

 which enables an animal to change or make 

 its environment; and improved intelligence, 

 which serves as a guide in all the contin- 

 gencies of life. The result of retrograde 

 evolution is the reverse of this. It is prob- 

 able that no progressive evolution could 

 have taken place without the presence of 

 sensation. As an illustration of retrogres- 

 sive evolution on a grand scale, we have 

 the vegetable kingdom. Originally freely 



moving amcebas, the ancestors of plants be- 

 came sessile or earth parasites. The result 

 is that they have become bound to their en- 

 vironment, which they cannot change. 

 They have therefore to suffer enormous de- 

 struction. To counteract this they have 

 developed equally enormous powers of re- 

 production. In fact, although the vegeta- 

 ble kingdom is essential to the existence of 

 the animal kingdom, for itself it has accom- 

 plished progress in but one direction, that 

 of reproduction. 



The contrast presented by the animal 

 kingdom is great, and as the result has 

 been man it is evident that the process has 

 been as a whole progressive. The element 

 of sensation at the bottom of it has been 

 probably the central directive point, like the 

 live bud on the apex of a tree. Though of 

 limited local distribution, it has led the 

 way, and all other modifications have fol- 

 lowed. 



The other x^roblem for solution to which I 

 have referred is that of inheritance. The 

 inheritance not only of the characters of 

 species, but of individual and family traits, 

 is commonly accepted as a fact. But many 

 things are not inherited, such as injuries to 

 the organism, except in very exceptional 

 cases, so that it has been questioned whether 

 any character acquired by the organism 

 during its life can be inherited. But so far 

 as regards certain characters already re- 

 ferred to as having been acquired by move- 

 ments of the parts, it is clearly proved that 

 they are inherited, as they are found in the 

 embryo before birth, and were therefore 

 inherited by the offspring directly from the 

 parents and were not produced by them- 

 selves. It is evident that the characters of 

 the vertebrate skeleton were acquired 

 through motion, or use, by gradual accre- 

 tions of modifications, and that these modi- 

 fications were inhei-ited by the successive 

 generations. Each generation added its 

 quota to the result, which thus steadily pro- 



