MODERN BIOLOGY 3x1 



His life-theory: life is motion 

 Lamarck begins his work Kecherches with a protest against that dry systema- 

 tization that is content with differentiating as many species as possible with- 

 out troubling to make a comprehensive survey of the connexion between the 

 life-forms in nature. Rather, he would start by regarding life in its entirety, 

 and he thereupon finds, in accordance with his conception referred to above, 

 that the most essential quality of life is motion. All that occurs in life is 

 motion; through it the organism strives to develop and to specialize the 

 organs; motion is also the absorption of nutriment, whereby the individual, 

 during its days of physical power, compensates for the losses caused by excre- 

 tion, whereas during the later period of life excretion becomes superior to the 

 power of absorbing nutriment, so that eventually death results; it is through 

 motion that development proceeds in every living being, the fluids of the 

 body making their way through the surrounding solid parts, with the result 

 that in these latter are formed organs which assume various functions, and 

 canals which convey nourishment to them.^ Thus is gradually formed not 

 only the individual, but also, step by step, all living beings of various types, 

 while the qualities that have been developed in the individual life-forms are 

 transferred by reproduction to the descendants. On this basis it is possible to 

 place all living beings in one series, beginning with the lowest and ending 

 with the highest. It is more instructive, however, to examine the organiza- 

 tion of animals in the opposite direction, in that, if we start from the highest 

 forms, we can follow the "degradation" that appears in the series, one organ 

 after another becoming changed, simplified, and finally disappearing. The 

 mammals are naturally the highest; they are the only creatures that really 

 produce their young alive; they possess milk-secretion, independent lungs, 

 and complete diaphragm. The birds come lower than the mammals, for they 

 lay eggs, their lungs are fixed, and they have no diaphragm. Below these two 

 warm-blooded animal groups come the reptiles, owing to their cold blood and 

 incompletely formed heart and lungs, which latter are in certain forms repre- 

 sented during earlier stages by gills (the batrachians, as is well known, were 

 still at that time grouped together with the reptiles); further, the two pairs 

 of extremities in these animals gradually disappear, wherefore the snakes, 

 which possess no extremities, are the lowest of the order of reptiles. Upwards, 

 again, the transition between reptiles and birds is formed by the Chelonia 

 (tortoises), while the then newly-discovered duck-billed platypus assumes 

 the same role between birds and mammals. The fishes, on the other hand, are 

 lower than the reptiles, for they have entirely lost lungs and extremities; 

 that is to say, their fins are not real extremities. With the transition from the 

 fishes downwards the backbone and the inner skeleton disappear from the 



^ This theory recalls a similar one of Caspar Friedrich Wolff's (Part II, p. 2.50), but it is 

 uncertain whether Lamarck knew his works — at any rate, he never quotes them. 



