388 SYNOPSIS 



VI. BRIEF DESCRIPTIONS OF TYPES OF THE HIGHER GROUPS OF 

 ANIMALS AND PLANTS IN TERMS OF POLYGORDIUS AND OF 

 THE FERN RESPECTIVELY. 



PAGE 



a. Animals. 



All are tripoblastic and coelomate. 



35. Starfish. 



Radially symmetrical : discontinuous dermal exo-skele- 

 ton : characteristic organs of locomotion (tube feet) in 

 connection with ambulacral system of vessels .... 305 



36. Crayfish. 



Metamerically segmented : segmented lateral append- 

 ages : differentiation of metameres and appendages : 

 continuous cuticular exo-skeleton discontinuously calci- 

 fied : gills as paired lateral offshoots of the body-wall : 

 heart as muscular dilatation of dorsal vessel : coelome 

 greatly reduced and its place taken by an extensive series 

 of blood-spaces : nervous system sunk in the mesoderm 

 and consisting of brain and ventral nerve-cord . . . . 310 



37. Mussel. 



Non-segmented : mantle formed as paired lateral out- 

 growths of dorsal region : foot as unpaired median out- 

 growth of ventral region : cuticular exo-skeleton in the 

 form of a calcified bivalved shell : gills as paired lateral 

 outgrowth of body-wall : heart as muscular dilatation of 

 dorsal vessel : coelome reduced to pericardium : nervous 

 system consists of three pairs of ganglia sunk in the 

 mesoderm . 316 



38. Dogfish. 



Metamerically segmented : differentiated into head, 

 trunk, and tail : trunk alone coelomate in adult : ap- 

 pendages as median (dorsal, ventral, and caudal) and 

 paired (pectoral and pelvic) fins : discontinuous dermal 

 exo-skeleton and extensive endo-skeleton of partially 

 calcified cartilage, including a chain of vertebral centra 

 below the nervous system replacing an embryonic noto- 

 chord : gills as pouches of pharynx opening on exterior : 

 heart as muscular dilatation of ventral vessel : hollow 

 dorsal nervous system not perforated by enteric canal 320 



/>. Plants. All exhibit alternation of generations and the series 

 shows the gradual subordination of the gamobium to the 

 agamobium. 



