234: haeckel's anthropogenie. 



taneously made by Cuvier from comparison of adult structure. 

 These observations led to the enunciation of the law -which bears his 

 name. " Development is from the general to the special ; " type of 

 development depends upon the relative position of the parts, grade 

 of development within a type on the amount of histological and 

 morphological differentiation. The former is the mechanical conse- 

 quence of heredity, the latter that of adaptation. 



The application of the cell-theory (1835) to ontogenesis was pro- 

 ductive of great advantage in the hands of Remak. He described 

 the mode of formation of the cellular layers from the unicellular 

 ovum in 1851, and by his investigations into the development of the 

 tissues from cells laid the foundation stone of histiogeny. 



The most important advance in late years has been the estab- 

 lishment of the occurrence of the two primary germ-layers in all 

 animals except protozoa (by Huxley, in 1849, medusae; Kowalevski, 

 1866, in amphioxus, ascidise, and afterwards in vermes, echinodermata, 

 arthropods; Haeckel, 1872, calcareous sponges; Ray Lankester, 

 molluscs). The absolute homology of these two germ-layers through- 

 out the whole animal series has been especially contended for by 

 Haeckel. 



The recognition of the causes of these facts has only taken place 

 since the appearance of Darwin's work on the "Origin of Species," but 

 the theory of evolution was scientifically sketched half a century 

 before that by Lamarck. 



The whole question of phylogenesis depends on that of the nature 

 and origin of Species. Linnseus first definitely applied the word in 

 1735, and grounded his belief in its nature on the Mosaic account of 

 the creation. 'No scientific theory of creation could then be formed, 

 for the science of palaeontology did not exist. Cuvier, however, the 

 father of palseontology, adhered to the Mosaic doctrine; but recog- 

 nizing the different sets of animals that had inhabited the world, he 

 explained these by different acts of creation and different revolutions 

 or cataclysms similar to the fiood. This catastrophic theory was 

 supported by the geological discoveries of the Wernerian school; but 

 the falsity of the inferences derived from these was first shown in 

 1830 by Lyell, whose uniformitarian theory is now universally 

 accepted. In spite of this, it was thirty years before the connection of 

 the present with the past inhabitants of the earth was scientifically 

 established by Darwin. 



