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The requested URL /mbrowse/msdb/OriginOfSpecies/description/is/I+HAVE+hitherto+sometimes+spoken+as+if+the+variations-+so+common+and+multiform+with+organic+beings+under+domestication,+and+in+a+lesser+degree+with+those+under+nature-+were+due+to+chance. This,+of+course,+is+a+wholly+incorrect+expression,+but+it+serves+to+acknowledge+plainly+our+ignorance+of+the+cause+of+each+particular+variation. Some+authors+believe+it+to+be+as+much+the+function+of+the+reproductive+system+to+produce+individual+differences,+or+slight+deviations+of+structure,+as+to+make+the+child+like+its+parents. But+the+fact+of+variations+and+monstrosities+occurring+much+more+frequently+under+domestication+than+under+nature,+and+the+greater+variability+of+species+having+wider+ranges+than+of+those+with+restricted+ranges,+lead+to+the+conclusion+that+variability+is+generally+related+to+the+conditions+of+life+to+which+each+species+has+been+exposed+during+several+successive+generations. In+the+first+chapter+I+attempted+to+show+that+changed+conditions+act+in+two+ways,+directly+on+the+whole+organisation+or+on+certain+parts+alone,+and+indirectly+through+the+reproductive+system. In+all+cases+there+are+two+factors,+the+nature+of+the+organism,+which+is+much+the+most+important+of+the+two,+and+the+nature+of+the+conditions.+ The+direct+action+of+changed+conditions+leads+to+definite+or+indefinite+results.+In+the+latter+case+the+organisation+seems+to+become+plastic,+and+we+have+much+fluctuating+variability. In+the+former+case+the+nature+of+the+organism+is+such+that+it+yields+readily,+when+subjected+to+certain+conditions,+and+all,+or+nearly+all+the+individuals+become+modified+in+the+same+way. It+is+very+difficult+to+decide+how+far+changed+conditions,+such+as+of+climate,+food,+&c.,+have+acted+in+a+definite+manner. There+is+reason+to+believe+that+in+the+course+of+time+the+effects+have+been+greater+than+can+be+proved+by+clear+evidence. But+we+may+safely+conclude+that+the+innumerable+complex+co-adaptations+of+structure,+which+we+see+throughout+nature+between+various+organic+beings,+cannot+be+attributed+simply+to+such+action. In+the+following+cases+the+conditions+seem+to+have+produced+some+slight+definite+effect:+E.+Forbes+asserts+that+shells+at+their+southern+limit,+and+when+living+in+shallow+water,+are+more+brightly+coloured+than+those+of+the+same+species+from+further+north+or+from+a+greater+depth;+but+this+certainly+does+not+always+hold+good.+ [[[[[images/Sea+Shell.jpg|Sea+Shell]]]]]/ was not found on this server.