xvi INVEETEBEATA 



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

 Oynthia partita as a type of the Uroohorda — 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 epioardium — The 

 formation of the stigmata— The development of the genital organs in Molgida — , 

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

 loides — The Development of Asoidiae compositae — The development of Pyrosoma 

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

 as a type of the Thaliaoea — The formation of the placenta — The development of 

 Doliolum — The development of buds in Uroohorda — Stolonial budding— The 

 organogeny of the Blastozooid — The Ascidiozooids of Pyrosoina — The buds of Salpa 

 and o'f 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 Cephalochorda . . . Page 568 



CHAPTEE 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 etfect of yolk and of maternal secretions — The 

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

 Metazoa . . . . . . . . . Page 649 



EEEATA 



Page 9, line 58, for "cell sap" read "cell and sap." 

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

 ,, 125, line22,/or " first micleua " read " nuclear matter of the sperm head. " 

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



