1. Turbellaria. *2. Scolecida. (Worms with a coelom, probably represented at the present day by _Balanoglossus_.) *3. Himatega. (Evolved from Scolecida by formation of dorsal nerve-tube and chorda, and resembling tailed larvae of Ascidians.) 4. Acrania. (With metameric segmentation. Including Amphioxus.) 5. Monorrhina. (Cyclostomes.) 6. Selachia. 7. Dipneusta. 8. Sozobranchia. (Amphibia with permanent gills.) 9. Sozura. (Tailed Amphibia.) *10. Protamnia. *11. Promammalia. 12. Marsupialia. 13. Prosimiae. 14. Menocerca. (Tailed apes.) 15. Anthropoides. 16. 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 evolution of Vertebrates is given in the _Systematic Phylogeny_ of 1895.[441] The ontogenetic and ancestral stages are arranged in parallel columns thus:-- Cytula. Cytaea (Protozoa). Morula. Moraea (Coenobium of Protozoa). Blastula. Blastaea (_Volvocina_, etc.). Depula (invaginated blastula). Depaea. Gastrula. Gastraea (cf. _Olynthus_, _Hydra_, and primitive Coelentera). Coelomula (with one pair Coelomaea (cf. _Sagitta_, _Ascidia_, of coelom-pockets). and primitive Helminthes). Chordula (with medullary Chordaea (_cf._ Ascidian larva and tube and chorda). larva of Amphioxus). Spondula (with segmented Prospondylus (Primitive Vertebrate). mesoderm). 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 coelom, which had been made in the interval of some twenty years.