460 THE GENERAL PRINCIPLES OF ZOOLOGY 



theory rests on the assumption that such variations are trans- 

 mitted to the offspring, and ever since this theory was pro- 

 pounded, scientists have been arrayed in two bands, the one 

 maintaining that such acquired characteristics can be trans- 

 mitted to offspring, the other that they cannot ; it is sufficient, 

 perhaps, to say that, however well the theory may account for 

 the development or the loss of various structures, it is extremely 

 doubtful whether any reported example of an acquired charac- 

 teristic being transmitted from the parent to the offspring has 

 been proven conclusively to be so. This theory is of much 

 interest, because to-day a minority of scientists adhere to it 

 under the name of Neo-Lamarckism. 



Thus many scientists came to recognize in the theory of de- 

 scent or evolution the only explanation of the succession of plant 

 and animal life on the earth, although it was not until the latter 

 half of the century that evolution was accepted by all scientists 

 and its principles employed in many other departments of 

 knowledge as well ; many theologians believe the real meaning 

 of creation to be the institution of the order of nature, and hence 

 do not hesitate to accept the evolutional}- theory. But although 

 there is universal belief in evolution, the manner in which it has 

 been brought about is still a moot point. 



Interest in the subject was reawakened in 1859 by Charles 

 Darwin, an English scientist, when he published his theory of 

 natural selection, a theory which commanded especial attention 

 because based upon years of careful observation and experi- 

 mentation. In order that an animal may in the course of 

 generations give rise to descendants of a very different tvpe it 

 is necessary that there should be individual variation, and that 

 this variation should be transmitted from parent to offspring ; 

 hence the center of interest in the search for the cause and 

 method of evolution is the individual animal or plant, that is to 

 say, the species, and so Darwin undertook to determine whether 

 species are constant or whether it is probable that one may 

 give rise to another. For il is perfectly evident that if new- 

 species may arise in this way, then the same process must give 

 rise to new genera, families, orders, classes, and types ; the 

 evolution of the larger groups takes care of itself provided we 

 can account for the evolution of the smallest. 



