348 



SCIENTIFIC THOUGHT. 



first brilliant attempt to fill up conjecturally the broken 

 lines of development and descent as the Darwinian con- 

 ception of living nature postulates them. 1 As a first 

 and daring approximation, they deserve to .have assigned 

 to them a prominent place in the history of the scien- 

 tific thought of our age. In elaborating his pedi- 

 grees, Professor Haeckel has taken up and more clearly 

 defined the analogy between the development of the 

 embryo in the higher organisms and the supposed transi- 

 tion from lower to higher forms which is found in the 

 classification of the genera or species of animals and 

 plants. He has termed this analogy the great law of 

 biogenesis, of the development of life in the individual 

 <Yo ov), and the species or tribe (TO QvXov), expressed 

 also as the parallelism of ontogenesis and phylogenesis. 

 Long before Darwin and the appearance of the theory of 

 descent this analogy 2 was pointed out in a restricted 



1 The later editions of the ' Origin 

 of Species ' contain the following 

 reference to Haeckel (6th ed., p. 

 381) : " Prof. Haeckel, in his ' Gen- 

 erelle Morphologic,' and in other 

 works, has brought his great know- 

 ledge and abilities to bear on what 

 he calls phylogeny, or the lines of 

 descent of all organic beings. In 

 drawing up the several series he 

 trusts chiefly to embryological char- 

 acters, but receives aid from homo- 

 logous and rudimentary organs, as 

 well as from the successive periods 

 at which the various forms of life 

 are believed to have first appeared 

 in our geological formations. He 

 has thus boldly made a great be- 

 ginning, and shows us how classi- 

 fication will in the future be 

 treated. " And Huxley (art. " Evo- 

 lution," p. 752) says : " Whatever 

 hesitation may not unfrequently 



be felt by less daring minds in 

 following Haeckel ill many of his 

 speculations, his attempt to sys- 

 tematise the doctrine of evolution, 

 and to exhibit its influence as the 

 central thought of modern biology, 

 cannot fail to have a far-reaching 

 influence on the progress of 

 science." 



2 As to the early anticipations of 

 this so-called "law of biogenesis," 

 they are given with more or less 

 completeness by many modern 

 writers, such as Huxley in his 

 article on Evolution (1878, 'Ency. 

 Brit.'), P. Geddes (ibid., art. "Re- 

 production "), Yves Delage ( ' L'HeY- 

 e"ditey &c., p. 159), J. A. Thomson 

 ('The Science of Life,' p. 133, &c.) 

 The most important earlier state- 

 ment is that quoted by Huxley 

 from Meckel's ' Entwurf einer Dar- 

 stellung der zwischen dem Embryo- 



