150 



THE VOYAGE OF H.M.S. CHALLENGER. 



Chorizocormua 

 Thylacium 



Synetyela. 



Good&ina. 



Amai^oclum 

 plidium 

 F^a/nmaplidium 



GRAPHIC HEPIIESENTATION OF THE PHYLOGENY OP THE TUXICATA. 



The annexed sclieme shuws diagrammatically the probable pliylogcny of the Tunicata. Tliis group of 

 animals is represented as being derived from the Protochordata (in the top left-hand corner of the page) at 

 the point A., a little way below the position of Ar.iphioxus. It liranchos out into a series of lines having a 

 tree-like form, and representing the various ancestral and existing groups of Tunicata. The names at the 

 ends of the lines stand for genera or small groups of genera. A few of the less important genera have been 

 omitted. The letters A. B. . . . 0. represent hypothetical ancestral forms of importance which can 

 be partially reconstructed from our knowledge of existing forms. In most cases they are placed at points 

 wliere two or more lines of descent diverged from one another. 



In this Phylogenetic Table all existing forms are represented as being at the endu of brandies or twigs. 

 In no case has the line representing the evolution of one group been allowed to pass through another group. 

 Finally, the whole figure may be regarded as a graphic representation of the present state of our knowledge 

 as to the affinities of the various groups of the Tunicata. 



