3X1 THE HISTORY OF BIOLOGY 



animal kingdom. Of the invertebrates, the molluscs stand highest, for they 

 have gills like the fishes and possess brain, nerves, and single-chambered 

 heart. Next to them come the Annelida, which Lamarck, after Cuvier, dis- 

 tinguishes from the worms, and which he has named; they likewise breathe 

 by means of gills, sometimes visible, sometimes concealed in the skin; more- 

 over, they possess a nervous system, a vascular system with red blood, and a 

 pair of extensions thereof corresponding to the heart. These are followed by 

 the crustaceans, also possessing gills and heart, but after them these latter 

 organs disappear from the animal kingdom. The spiders come next; because 

 they have a concentrated respiratory system and emerge from the egg in the 

 same form as they retain afterwards, they are above the insects, which pos- 

 sess scattered tracheae and undergo metamorphosis. With these animals, in 

 Lamarck's view, sexual reproduction disappears from the animal kingdom. 

 Thus, the worms, which follow next in the series, are reproduced by gemma- 

 tion; as a matter of fact, they may possess a nervous system and tracheas. 

 With them disappear visual organs and nervous system from the animal king- 

 dom. The next class is the Radiata, another systematic creation of Lamarck's; 

 these animals lack visual organs, but possess organs of generation — though 

 sexless — ■ and are thereby distinguished from the polypi, which possess no 

 organs at all. 



Lamarck having thus classified the animals in a series on a basis of the 

 absence or presence of certain principal organs, he goes on to state that the 

 sequence thus formed does not refer to the separate animal individuals, but 

 to the great masses of animals that form one entire class; within such a class 

 it is possible that, owing to dissimilarities in less essential organs, ramifica- 

 tions may take place in various directions, but the above arrangement, which 

 has been made in the animal classes on the basis of the structure of the most 

 vital organs, is presented with such certainty that "no enlightened natural 

 scientist will be able to produce another." It shows how, the higher we come 

 in the series, the greater becomes the specialization in the organs, while the 

 lower we go, the simpler we find the organs becoming and the wider their 

 functions. On this ever-increasing specialization of the organs Lamarck now 

 bases his theory of how the various life-forms have arisen, a theory which at 

 the very outset he formulates as follows: "It is not the organs — that is to 

 say, the form and character of the animal's bodily parts — that have given 

 rise to its habits and peculiar properties, but, on the contrary, it is its habits 

 and manner of life and the conditions in which its ancestors lived that has 

 in the course of time fashioned its bodily form, its organs, and its qualities." 

 He seeks to prove this basic argument by innumerable examples: moles and 

 blind mice have lost their sight as a result of living underground for several 

 generations, the ant-bear its teeth through swallowing its food whole; 

 waders have acquired long legs and long neck through stretching those parts 



