SUMMAR Y OF ' PHILOSOPHIE ZOOLOGIQ UE! 289 



of Species/ Mr. Darwin well confirms this when he 

 says, " In large genera the species are apt to be closely, 

 but unequally, allied together, forming little clusters 

 round other species." 



" A longer time," says Lamarck, " and a greater in- 

 fluence of surrounding conditions, is necessary in order 

 to modify interior organs. Nevertheless we see that 

 Nature does pass from one system to another without 

 any sudden leap, when circumstances require it, pro- 

 vided the systems are not too far apart. Her method 

 is to proceed from the more simple to the more com- 

 plex.* 



"She does this not only in the race, but in the 

 individual." Here Lamarck, like Dr. Erasmus Dar- 

 win, shows his perception of the importance of em- 

 bryology in throwing light on the affinities of animals 

 as since more fully insisted on by the author of the 

 ' Vestiges of Creation,' and by Mr. Darwin, \ as well as 

 by other writers. " Breathing through gills is nearer 

 to breathing through lungs than breathing through 

 trachea is. Not only do we see Nature pass from gills 

 to lungs in families which are not too far apart, as may 

 be seen by considering the case of fishes and reptiles ; 

 but she does so during the existence of a single in- 

 dividual, which may successively make use both of the 

 one and of the other system. The frog while yet a tad- 

 pole breathes through gills; on becoming a frog it 

 breathes through lungs ; but we cannot find that 

 Nature in any case passes from trachea to lungs." \ 



* * Phil. Zool.,' torn. i. p. 123. f ' Origin of Specie^ chap. xiv. 

 \ ' Phil. Zool.,' torn. i. p. 123. 



U 



