294 THE GERM-LAYERS AND EVOLUTION 



9. Sozura. (Tailed Amphibia.) 

 *io. Protamnia. 

 *ii. Promammalia. 



12. Marsupialia. 



13. Prosimue. 



14. Menocerca. (Tailed apes.) 



15. Anthropoides. 



1 6. Pithecanthropi. 



17. Homines. 



It will be noticed that except for the hypothetical forms 

 (marked with an asterisk), which are themselves generalised 

 classificatory groups, the ancestral forms belong to long- 

 recognised classes. The whole course of the evolution 

 follows well-worn systematic lines. This is typical of 

 Haeckel's phylogenetic speculations. 



A more abstractly 'morphological scheme of the evolu- 

 tion of Vertebrates is given in the Systematic Phylogeny Ql 

 1 895.* The ontogenetic and ancestral stages are arranged in 

 parallel columns thus : 



Cytula. Cytrca (Protozoa). 



Morula. Monea (Coenobium of Protozoa). 



Blastuhi. l!lubta;a (Volvocina, etc.). 



Depula (invaginated bias- Deprea. 



tula). 



Gastrula. Gastrrea (cf. Olynthiis, Hydra, and primi- 

 tive Coclentera). 



Cculomula (with one pair Cceh>m;ea (cf. Sagitta^ Ascidia, and 



of adom-pockets). primitive Helminthes). 



Chordula (with medullary Chorda^a (cf. Ascidian larva and larva of 



tube and chorda). Amphioxus). 



Spondula (with segmented Prospondylus (Primitive Vertebrate). 



mesodcrm). 



This scheme differs from the earlier one chiefly in taking 

 into account certain advances, notably as regards the cytology 

 of the fertilised ovum and the true nature of the cculom, 

 which had been made in the interval of some twenty years. 



Hieckel's Gastnua theory, though it exercised a great 

 influence upon the subsequent trend of phylogenetic 

 speculation, was by no means universally accepted tcllc ijncllc. 

 Opinions differed considerably as to the primitive mode of 



i.- I'hylogcnie, iii., p. 41, Dcrlin, 



