xvi INVERTEBEATA 



The ancestral meaning of 'the asymmetry of the larva The development of 

 Cynthia partita as a type of the Urochorda Its cell-lineage and the segregation 

 of coloured organ-forming substances The process of gastrulation The develop- 

 ment of the nervous system The free-swimming larva of simple Ascidians and 

 its metamorphosis The formation of heart, pericardium, and epicardium The 

 formation of the stigmata The development of the genital organs in Molgula 

 Experiments on the eggs of simple Ascidians Development of Molgula ampul- 

 loides The Development of Ascidiae compositae The development of Pyrosoma 

 as a type of the Ascidiae luciae The Cyathozooid The development of Salpa 

 as a type of the Thaliacea The formation of the placenta The development of 

 Doliolum The development of buds in Urochorda Stolonial budding The 

 organogeny of the Blastozooid The Ascidiozooids of Pyrosoma The buds of Salpa 

 and of Doliolum Pallial budding in the Botryllidae Budding in Diplosomidae 

 The reason for the different organogeny in the bud and in the larva The 

 affinities of the Urochorda with the Gephalochorda . . . Page 568 



CHAPTER XVIII 



SUMMARY 



Physiological explanation of recapitulation Evidence in favour of the possibility of 

 the inheritance of functional adaptations Secondary modifications of the re- 

 capitulatory life -history The effect of yolk and of maternal secretions The 

 modus operandi of organ-forming substances Sketch of the ancestral history of 

 Metazoa . . . Page 649 



EERATA 



Page 9, line 38, for "cell sap " read " cell and sap." 



,, 61, lines 5 and 6, for "medusa S. apicata" read "medusa of S. apicata." 

 ,, 125, line 22, for "first nucleus " read " nuclear matter of the sperm head." 

 ,, 126, line 4, for " broken in two " read " broken into." 



