THE HISTORY OF OUR SPECIES. 83 



in 1859, and Fritz Mutter had endeavoured to prove 

 it as regards the Crustacea in the able little work, 

 Facts and Arguments for Darwin (1864) . My own task 

 has been to prove the universal application and the 

 fundamental importance of the biogenetic law in a 

 series of works, especially in the Biology of the Calci- 

 spongice (1872), and in Studies of the Gastrcea Theory 

 (1873-1884). The theory of the homology of the 

 germinal layers and of the relations of palingenesis 

 to cenogenesis which I have exposed in them has 

 been confirmed subsequently by a number of works 

 of other zoologists. That theory makes it possible to 

 follow nature's law of unity in the innumerable varia- 

 tions of animal embryology ; it gives us for their 

 ancestral history a common derivation from a simple 

 primitive stem-form. 



The far-seeing founder of the theory of descent, 

 Lamarck, clearly recognised in 1809 that it was of 

 universal application ; that even man himself, the 

 most highly developed of the mammals, is derived 

 from the same stem as all the other mammals ; and 

 that this in its turn belongs to the same older branch 

 of the ancestral tree as the rest of the vertebrates. 

 He had even indicated the agencies by which it might 

 be possible to explain man's descent from the apes as 

 the nearest related mammals. Darwin, who was, 

 naturally, of the same conviction, purposely avoided 

 this least acceptable consequence of his theory in his 

 chief work in 1859, and put it forward for the first 

 time in his Descent of Man in 1871. In the mean- 

 time (1863) Huxley had very ably discussed this most 

 important consequence of evolution in his famous 

 Place of Man in Nature. With the aid of comparative 

 anatomy and ontogeny, and the support of the facts of 



