TRANSMISSION OF MODIFICATIONS 415 



least (temperature, food, poisons, and many chemicals not 

 poisons), both evident and easy to understand ; in others it is 

 obscure and uncertain to the last degree. 



Degeneracy and origin contrasted. Of one thing we are cer- 

 tain : characters are disappearing before our very eyes, and 

 whole races are becoming extinct. What does this mean ? Is the 

 world growing poorer in possibilities ? Is specialization realized 

 only at the expense of lessened adaptability to new conditions 

 later on ? If a part or a character now useless degenerates and 

 disappears will it ever come back, or will a new one arise to take 

 its place if necessity for its presence should return ? 



These are large questions questions that we cannot answer, 

 but that we must think about and take into consideration in the 

 studying and answering of easier and smaller questions. 



In the meantime we will remember that soles, flounders, and 

 the flatfishes generally are developing a new style of living, 1 and 

 that their eyes are taking a new position with reference to the 

 other body parts. We will not forget that all animals that live 

 in (under) the water, if of much size, are of one general shape, 

 the shape of least resistance to water. That this is independ- 

 ent of selection is shown in the history of the whale and of the 

 few land mammals that took to the water and whose transforma- 

 tion must have been comparatively recent. 



We will remember that, while most " new characters " are 

 but new combinations and different adjustments of old ones, 

 there is, after all, progressive development showing the infusion 

 of something practically new and different. Higher life differs 

 from lower in kind as well as in degree. That it springs from 

 the lower is certain, and that something has been added in the 

 process is no less certain. 



The world is full of lowly forms of life. The species of single- 

 celled organisms that are known probably far outnumber existing 



1 These fishes, of which there are a number of species, are symmetrical, or 

 nearly so, in the embryo and for a little time afterward, so that at first they swim 

 like any other fish. The swimming bladder is defective, however, and shortly they 

 tarn to one side and lie on the bottom, generally left side down, though some 

 individuals are reversed. In this position the left (now lower) eye travels upward 

 toward the other side, until the two eyes lie side by side on the right, now the 

 upper, side. 



