14 THE EVOLUTION OF CONTINUITY 



PA8E 



out of nerve tracts towards the brain cortex — The situation of 

 cortical motor areas in the vertebrate brain ; suggested funda- 

 mental explanation — The correction of deviation in Birds and 

 Quadrupeds. 



CHAPTER XXVI 

 Alternation of Generations. Parthenogenesis . . 240 



Alternation of generations : usual definition — Term itself inappro- 

 priate — Alternation of intermediate and Terminal Cycle-stages — 

 this alternation summarised in the successive types of Individual 

 Continuity. 



Parthenogenesis — the common definition not satisfactory — The 

 process can only be exhibited by a part of an Individual — Sug- 

 gestion that the true parthenogenetic cell is never an ovum, but 

 always an intermediate cycle-stage — Loeb's experiment—" non- 

 specific fertilisation." 



Chapteb XXVII 



Karyokinesis 248 



The phenomena are exhibitions of Attraction and Repulsion in 

 action — Three forms of Karyokinesis : with double chromosomes, 

 with single chromosomes, and as it occurs in polar extrusion — 

 Double chromosome karyokinesis ; the three main stages of 

 the process, and some suggestions regarding their significance. 

 Extrusion of Polar Bodies, a form of Karyokinesis — the process 

 described — its significance a mystery. 



Chapter XXVIII 



Abnormal Growth. Tumours 260 



The explanation of abnormal growth to be looked for in the light 

 of the laws of normal growth — Two aspects of the question. 

 Classification of Tumours — The characters of the main varieties — 

 The problem viewed in the light of Arrest, and Release from 

 Arrest — Natural Arrest — Unnatural Arrest. 



Tumours which are the result of Escape from Unnatural Arrest — 

 (1) when the unnatural arrest is of late application ; (2) when it 

 is applied early — In the former case the tumours are typical, and 

 their growth not completely uncontrolled ; in the latter case 

 growth is uncontrolled and atypical — The possibility of a " tumour- 

 Individual " and of "tumour-gametes" — Cancer-bodies — Secondary 

 growth. 



Tumours whose origin is due to Escape from Natural Arrest ; 

 their nature — The healing of wounds, and the regeneration of 

 tissue — Natural Arrest and Control — The restraining influence of 

 connective-tissue on overlying epithelium — Experiments of 

 Champy — The origination of epitheliomata ; some speculations — 

 Cell-damage or breach of Continuity probably always precedes the 

 formation of such tumours — The stroma of malignant tumours. 



Index 275 



