276 ON THE STUDY OF BIOLOGY X 



sophers, turns out to be substantially correct. 

 More than this, when biologists pursue their 

 investigations into the vegetable world, they find 

 that they can, in the same way, follow out the 

 structure of the plant, from the most gigantic and 

 complicated trees down through a similar series 

 of gradations, until they arrive at specks of 

 animated jelly, which they are puzzled to distin- 

 guish from those specks which they reached by 

 the animal road. 



Thus, biologists have arrived at the conclusion 

 that a fundamental uniformity of structure per- 

 vades the animal and vegetable worlds, and that 

 plants and animals differ from one another simply as 

 diverse modifications of the same great general plan. 



Again, they tell us the same story in regard to 

 the study of function. They admit the large and 

 important interval which, at the present time, 

 separates the manifestations of the mental faculties 

 observable in the higher forms of mankind, and 

 even in the lower forms, such as we know them, 

 from those exhibited by other animals ; but, at 

 the same time, they tell us that the foundations, 

 or rudiments, of almost all the faculties of man 

 are to be met with in the lower animals ; that 

 there is a unity of mental faculty as well as of 

 bodily structure, and that, here also, the difference 

 is a difference of degree and not of kind. I said 

 " almost all," for a reason. Among the many dis- 

 tinctions which have been drawn between the 



