10 LECTUKES ON BIOLOGY 



use, though what the forces were that affected variation and 

 adaptation was a question to which he was unable to give a 

 satisfactory answer. 



In Germany it was above all Goethe who advocated the 

 theory of descent in numerous important works, but the most 

 prominent predecessor of the great Darwin is doubtless Jean 

 Baptiste Lamarck. In vain Lamarck waited during a long 

 laborious life, the last seventeen years of which were spent in 

 total blindness, for the recognition of his contemporaries. His 

 numerous writings remained either unknown or were misunder- 

 stood. Only now, when almost a century has passed since his 

 death, it seems as if his work shall at last receive its due share 

 of praise, for during recent years a strong tendency has shown 

 itself not only among botanists but also zoologists to turn back 

 to the teachings of this great, unhappy man. 



According to Lamarck, the simplest organisms originated by 

 spontaneous generation (Urzeugung) out of inorganic matter 

 when the earth had sufficiently cooled to permit of the existence 

 of life. In the course of vast periods the living species of 

 plants and animals developed out of these lowest forms by 

 slow and gradual changes. The last and highest development 

 was man. In contrast to modern biogenetic conceptions which 

 represent the evolution of the organic world in the shape of ;i 

 tree of many branches, Lamarck conceived the animal world as a 

 uniform series of stages ascending from the unicellular protozoon 

 to man. 



Lamarck perceived the cause of the changes in the organic 

 world and the origin of new species to be that with the pro- 

 gressing cooling of the earth's crust the conditions of life for both 

 plants and animals underwent a continuous if gradual change. 

 If the organisms had not possessed the faculty of adapting them- 

 selves to the new conditions it would have been inevitable that 

 after the lapse of thousands or millions of years forms that once 

 were well adapted would cease to be so and perish. But we can 

 clearly see that the animals of the present day are as well adapted 

 to present conditions as were the animals of earlier periods to the 

 conditions then existing. It is, therefore, indubitable that hand 

 in hand with the changes of the earth there must have gone on 

 a continuous change in the organisms. Hence the question arises, 



