Vlll CONTENTS. 



CAUSE VAKIABILITT — CROSSING AS A CAUSE OF THE APPEARANCE 

 OF NEW CHARACTERS — VARIABILITY FROM THE COMMINGLING OF 

 CHARACTERS AND FROM REVERSION — ON THE MANNER AND PERIOD 

 OF ACTION OF THE CAUSES WHICH EITHER DIRECTLY, OR IN- 

 DIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE VARIA- 

 BILITY Pages 237-259 



CHAPTEE XXIII. 



DIRECT AND DEFINITE ACTION OF THE EXTERNAL CON- 

 DITIONS OF LIFE. 



SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE ACTION OF 

 CHANGED CONDITIONS, IN SIZE, COLOUR, CHEMICAL PROPERTIES, 

 AND IN THE STATE OF THE TISSUES — LOCAL DISEASES CON- 

 SPICUOUS MODIFICATIONS FROM CHANGED CLIMATE OR FOOD, ETC. 

 — PLUMAGE OF BIRDS AFFECTED BY PECULIAR NUTRIMENT, AND 

 BY THE INOCULATION OF POISON — LAND-SHELLS — MODIFICATIONS OF 

 ORGANIC BEINGS IN A STATE OF NATURE THROUGH THE DEFINITE 

 ACTION OF EXTERNAL CONDITIONS — COMPARISON OF AMERICAN 



AND EUROPEAN TREES — GALLS — EFFECTS OF PARASITIC FUNGI 



CONSIDERATIONS OPPOSED TO THE BELIEF IN THE POTENT IN- 

 FLUENCE OF CHANGED EXTERNAL CONDITIONS— PARALLEL SERIES 

 OF VARIETIES — AMOUNT OF VARIATION DOES NOT CORRESPOND 

 WITH THE DEGREE OF CHANGE IN THE CONDITIONS — BUD-VARIA- 

 TION — MONSTROSITIES PRODUCED BY UNNATURAL TREATMENT — 

 SUMMARY 260-282 



CHAPTER XXIV. 



LAWS OF VARIATION — USE AND DISUSE, ETC. 



NISCS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE ORGANISA- 

 TION — ON THE EFFECTS OF THE INCREASED USE AND DISUSE OF 

 ORGANS — CHANGED HABITS OF LIFE — ACCLIMATISATION WITH 

 ANIMALS AND PLANTS — VARIOUS METHODS BY WHICH THIS CAN 

 BE EFFECTED — ARRESTS OF DEVELOPMENT — RUDIMENTARY ORGANS. 



283-310 



